The Microsoft SharePoint Team announced that the SharePoint SP2 service pack by mistake activates a 180-day countdown.
“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 team is working as hard as possible to release a hotfix to address the issue.
The Work around is also known: Re-enter the Product ID numbers on the Convert License Type page in Central Administration.
More information at the Microsoft SharePoint team site.