SECOND AMENDMENT AND WAIVER TO CREDIT AGREEMENT

Exhibit 10.8.2

A RTHUR J. G ALLAGHER & C O .

S ECOND A MENDMENT AND W AIVER TO C REDIT A GREEMENT

Ladies and Gentlemen:

This Second Amendment and Waiver to Credit Agreement dated as of March 4, 2005 (herein, the “Amendment” ) is entered into by and between the undersigned, Arthur J. Gallagher & Co., a Delaware corporation (the “Borrower” ), the Banks and the Agent. Reference is hereby made to that certain Credit Agreement dated as of July 21, 2003 (said Credit Agreement, as amended prior to the date hereof, being referred to herein as the “Credit Agreement” ) between the Borrower, Citibank, N.A., Bank of America, N.A., LaSalle Bank National Association, Barclays Bank Plc, Union Bank of California, N.A., U.S. Bank National Association, Fifth Third Bank (Chicago), Comerica Bank, PNC Bank and Harris Trust and Savings Bank, individually and as Agent. All capitalized terms used herein without definition shall have the same meanings herein as such terms have in the Credit Agreement.

The Borrower has requested that the Banks amend certain representations contained in the Credit Agreement and waive certain potential Defaults or Events of Default arising by reason of the Utah Verdict and the Related Accounting Treatment (each as hereinafter defined), and the Banks are willing to do so under the terms and conditions set forth in this Amendment.

S ECTION 1. A MENDMENTS .

Subject to the satisfaction of the conditions precedent set forth in Section 3 below, the Credit Agreement shall be and hereby is amended as follows:

1.1. The definition of the term “L/C Commitment” appearing in Section 6.1 of the Credit Agreement shall be amended and restated in its entirety to read as follows:

“ “L/C Commitment” means $125,000,000, as such amount may be reduced pursuant to the terms hereof.”

1.2. Section 7.6 of the Credit Agreement shall be amended and restated in its entirety to read as follows:

“ Section 7.6. No Material Adverse Change. Since December 31, 2004, except as previously disclosed in the Borrower’s Form 8-K filed with the SEC on February 14, 2005, there has been no change in the condition (financial or otherwise) or business prospects of the Borrower and its Subsidiaries taken as a whole which could reasonably be expected to have a Material Adverse Effect.”

1.3. Section 7.9 of the Credit Agreement shall be amended and restated in its entirety to read as follows:

“ Section 7.9. Litigation and Other Controversies Except as otherwise disclosed in (i) the Borrower’s financial statements heretofore delivered to the Agent and (ii) the Borrower’s Form 8-K filed with the SEC on February 14, 2005, there is no litigation or governmental proceeding or labor controversy pending, nor to the knowledge of the Borrower threatened, against the Borrower or any of its Subsidiaries which could reasonably be expected to have a Material Adverse Effect.”

S ECTION 2. W AIVERS .

On February 11, 2005, a jury in the Fourth District Court for the State of Utah rendered a verdict against AJG Financial Services, Inc. ( “AJGFS ”), a Material Wholly-Owned Subsidiary of the Borrower, in favor of Headwaters Incorporated in the approximate