Occasionally when you install Service Pack 2 on a MOSS installation it will reset the license code so that SharePoint thinks it is an evaluation copy that will expire in 180 days.  It doesn't actually break any functionality, at least not until the 180 days is up.  But it can be a bit disconcerting if you look at the licensing.  You can read more about the problem in the following KnowledgeBase article:

 

 

The SharePoint product team issued a Hot Fix last night that corrects the problem.  The Hot Fix can be applied either before or after installing SP2.  They are also working on getting the Hot Fix built right into the download of SP2, but that will take about 4 weeks before the download site is updated.  In the meantime you can download the hot fixes in the following locations: