I have just read about this horrible bug for MOSS Service Pack 2 (SP2) that affects all customers that have deployed it for SharePoint Server 2007. While you install this version of SP2 it actually activates product expiration date in your legit copy as if it is for 180 day trial. This is pain for most of the customers as they may not be aware about this issue and may have trouble identifying what went wrong unless they read about this bug or they call MS to solve this.
As of today there is only manual work around available to resolve this issue and as per MSDN Blog MS is working to resolve this issue with hotfix. The manual workaround is to re-entering the Product ID number (PID) on the Convert License Type page in Central Administration.
More information here http://blogs.msdn.com/sharepoint/archive/2009/05/21/attention-important-information-on-service-pack-2.aspx