This can be a little bit alarmist but did you read this post if it was not this title? :-) But be confident: bug is there and the solution also.

During the installation of SP2, a product expiration date is improperly activated. This means SharePoint will expire as though it was a trial installation 180 days after SP2 is deployed. The activation of the expiration date will not affect the normal function of SharePoint up until the expiration date passes. Furthermore, product expiration 180 days after SP2 installation will not affect customer’s data, configuration or application code but will render SharePoint inaccessible for end-users.

The way to modify Product ID is described in this KB: http://support.microsoft.com/default.aspx/kb/971620 

More information: http://blogs.msdn.com/sharepoint/archive/2009/05/21/attention-important-information-on-service-pack-2.aspx