The long awaited fix for the product key issue that cropped up after Service Pack 2 is now out.  You can find more information at the following KB:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;971620

Download locations:

• 32-bit version: http://download.microsoft.com/download/2/F/5/2F51AB71-1325-49D2-9CB9-18DEC4780E99/office2007-kb971620-fullfile-x86-glb.exe
• 64-bit version: http://download.microsoft.com/download/5/B/B/5BBD34A9-C528-42B0-8A5F-9A8997B25C32/office2007-kb971620-fullfile-x64-glb.exe