If you ran into the expired license issue after applying the Service Pack 2, you will be happy to know Microsoft has released an update to resolve the issue.
Quote from the SharePoint Team Blog:
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.
Here is the link to the Knowledge Base article: http://support.microsoft.com/kb/971620 (“When you install the 2007 Microsoft Office servers Service Pack 2, the product expiration date is activated incorrectly”)