Following this post: Project Server 2007: License type set to trial after loading Office Server Service Pack 2 (SP2), please find an important update from the SharePoint team:
The public update to fix this issue is available for customers to download. If you have any questions please send them here.
Service Pack 2 Update.
The public update for the Service Pack 2 expiration date issue is now available for download.
The update can be applied before or after Service Pack 2 installation. If the update is applied prior to installing Service Pack 2 it will prevent the expiration date from being improperly activated during installation of Service Pack 2, if it is applied after Service Pack 2 it will remove the expiration date incorrectly set during installation of Service Pack 2.
The update is applicable to all of the products that this issue affected (see the list in the KB linked below).
Installation instructions and download links for x86 and x64 are available in this KB: http://support.microsoft.com/kb/971620
The direct download link for x86 is: http://download.microsoft.com/download/2/F/5/2F51AB71-1325-49D2-9CB9-18DEC4780E99/office2007-kb971620-fullfile-x86-glb.exe
We will be updating the existing Service Pack 2 download package with a new package that includes this fix within the next 4-6 weeks.