We recently discovered that the VPCs we distributed as part of the VS2008 Beta2 release will expire on Thursday, November 1, 2007, much earlier than we had originally expected. Since the timeout is at the OS level, we cannot automatically extend the timeout period. As such we are currently in the process of reissuing the VPCs and expect to make them available early next week.
In the meantime, for anyone that has stored information in TFS that they need to access moving forward, we recommend that you immediately backup the TFS databases in preparation to move them to the updated VPCs. For information to complete these steps, please refer to the documentation on Moving Team Foundation Server.
We're still working on additional guidance to respond to this situation. As more information becomes available, I'll post it here.
Update - please see my latest post on this topic: http://blogs.msdn.com/jeffbe/archive/2007/10/27/update-on-expiring-vs2008-beta2-vpcs.aspx