Microsoft has released this important announcement about the recent releases of Service Pack 2 for MOSS:
We take product quality seriously and make every effort to avoid and resolve issues that adversely impact our customers. Unfortunately, we have recently discovered a bug with Service Pack 2 (SP2) that affects all customers that have deployed it for SharePoint Server 2007.
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.
We are working to release a hotfix to automatically fix this issue. A manual work-around is currently available and involves customers re-entering their Product ID number (PID) on the Convert License Type page in Central Administration. For more information and detailed steps please read this KB article.
We want to assure our customers that this issue does not impact data integrity or their SharePoint deployment in any other way.
For your convenience, below are some answers to questions that you may have and we will update this blog post with a link to the hotfix as soon as it's available.
We apologize for any inconvenience this issue may cause you.
Note, this is only for MOSS (and other products like Project Server 2007) but WSS installations are not affected. You can read the full blog post here which contains some additional Q&A.