Microsoft has released a fix for the SP2 problem that reverts the license into a Trial version after installing Service Pack 2.
More details can be found in the following KB article:
971620 - When you install the 2007 Microsoft Office servers Service Pack 2, the product expiration date is activated incorrectly
For your convenience here are the download links for the fix:
- 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