If you have downloaded and installed the Service Pack, please take note that Service Pack 2 will reset your product license key and product expiration date as though you are running on a trial license, which will expire in 180 days.  Though the expiration date will not affect the functionality of SharePoint until the expiration date.

For more information on this, check out the post by the SharePoint Team at:

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