If you reboot your Team Foundation Server machine one day, and then get some errors such as:
A Catastrophic Failure with ADAM, Access Denied when starting BISGSS, or a COMException “The server is not operational“, you might want to read my problems:

http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=16246

In the end, I set Everyone to Full Control of the HKLM\SYSTEM\CurrentControlSet\VSS key, rebooted, and things went away.