SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13D (RULE 13d-101) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13D-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO RULE 13D-2(a) (AMENDMENT NO. 3) ACM Government Opportunity Fund, Inc. -------------------------------------------------------------------------------- (Name of Issuer) Common Stock -------------------------------------------------------------------------------- (Title of Class of Securities) 000918 102 -------------------------------------------------------------------------------- (CUSIP Number) Michael A. Conway Aon Advisors, Inc. 200 East Randolph Drive Chicago, Illinois 60601 (312) 381-3000 -------------------------------------------------------------------------------- (Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications) April 4, 2003 -------------------------------------------------------------------------------- (Date of Event which Requires Filing of this Statement) If the filing person has previously filed a statement on Schedule 13G to report the acquisition which is the subject of this Schedule 13D, and is filing this schedule because of Rule 13d-1(b)(3) or (4), check the following box / /. Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Rule 13d-7(b) for other parties to whom copies are to be sent. (Continued on following pages) PAGE 1 OF 8 CUSIP NO. 000918 102 SCHEDULE 13D PAGE 2 OF 8 -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) AON CORPORATION 36-3051915 -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) / / (b) / / -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS (See Instructions) Not Applicable -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 4,390,736 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 4,390,736 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,390,736 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 34.5% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) HC, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 SCHEDULE 13D PAGE 3 OF 8 -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) AON ADVISORS, INC. 54-1392321 -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) / / (b) / / -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS (See Instructions) Not Applicable -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Virginia -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 4,390,736 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 4,390,736 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,390,736 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 34.5% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) IA, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 SCHEDULE 13D PAGE 4 OF 8 -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) COMBINED INSURANCE COMPANY OF AMERICA 36-2136262 -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) / / (b) / / -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS (See Instructions) WC -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Illinois -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 4,360,308 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 4,360,308 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,360,308 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 34.2% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) IC, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 SCHEDULE 13D PAGE 5 OF 8 -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) COMBINED SPECIALTY INSURANCE COMPANY -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (See Instructions) (a) / / (b) / / -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 SOURCE OF FUNDS (See Instructions) WC -------------------------------------------------------------------------------- 5 CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) or 2(e) / / -------------------------------------------------------------------------------- 6 CITIZENSHIP OR PLACE OF ORGANIZATION Illinois -------------------------------------------------------------------------------- NUMBER OF 7 SOLE VOTING POWER 0 SHARES ----------------------------------------------------- BENEFICIALLY 8 SHARED VOTING POWER 30,428 OWNED BY ----------------------------------------------------- EACH 9 SOLE DISPOSITIVE POWER 0 REPORTING ----------------------------------------------------- PERSON WITH 10 SHARED DISPOSITIVE POWER 30,428 -------------------------------------------------------------------------------- 11 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 30,428 -------------------------------------------------------------------------------- 12 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions) / / -------------------------------------------------------------------------------- 13 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 0.2% -------------------------------------------------------------------------------- 14 TYPE OF REPORTING PERSON (See Instructions) IC, CO -------------------------------------------------------------------------------- CUSIP NO. 000918 102 This Amendment No. 3 (this "Amendment") amends and supplements the Schedule 13D filed with the Securities and Exchange Commission on December 10, 1999 (the "Schedule 13D") by Aon Corporation, a Delaware corporation ("Aon"), Aon Advisors, Inc., a Virginia corporation ("Advisors"), Combined Insurance Company of America, an Illinois corporation ("CICA"), and Combined Specialty Insurance Company, an Illinois corporation, formerly known as Virginia Surety Company ("CSIC", and together with Aon, Advisors and CICA, the "Filing Persons"). The Schedule 13D and this Amendment relate to the Common Stock (the "Common Stock") of ACM Government Opportunity Fund, Inc. (the "Issuer"). Capitalized terms used but not defined herein have the meanings ascribed to such terms in the Schedule 13D. Item 7 of the Schedule 13D is hereby amended and restated in its entirety as follows: Page 6 of 8 ITEM 7. MATERIAL TO BE FILED AS EXHIBITS A. Investment Advisory Agreement dated May 1, 1992 between Aon Advisors and CICA (incorporated by reference to the Schedule 13D filed by the Filing Persons on December 10, 1999) B. Investment Advisory Agreement dated May 1, 1992 between Aon Advisors and CSIC (incorporated by reference to the Schedule 13D filed by the Filing Persons on December 10, 1999) C. Joint Filing Agreement dated December 10, 1999 among each of the Filing Persons (incorporated by reference to the Schedule 13D filed by the Filing Persons on December 10, 1999) D. Letter from CICA and CSIC to the Issuer dated December 27, 1999 (incorporated by reference to Amendment No. 1 to the Schedule 13D filed by the Filing Persons on December 27, 1999) E. Letter from CICA and CSIC to the Issurer dated March 7, 2000 (incorporated by reference to Amendment No. 2 to the Schedule 13D filed by the Filing Persons on March 16, 2000) Page 7 of 8 SIGNATURE After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct. AON CORPORATION Date: April 7, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway Senior Vice President and Senior Investment Officer AON ADVISORS, INC. Date: April 7, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway President COMBINED INSURANCE COMPANY OF AMERICA Date: April 7, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway Senior Vice President COMBINED SPECIALTY INSURANCE COMPANY Date: April 7, 2003 /s/ Michael A. Conway ------------------------ By: Michael A. Conway Senior Vice President Page 8 of 8