During the installation of Service Pack 2 (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.

Microsoft is working on a HotFix for this issue, and since this issue will only present itself in 6 months time, this should not hinder you deploying SP2 now.

More information can be found on the SharePoint Team Blog and the KB Article