Typically, one of the first things installed on a Terminal or Citrix server, is the User Profile Hive Cleanup (UPHClean)service. UPHClean ensures user sessions are completely terminated when a user logs off.
UPHClean fails to install on Windows Server 2008 as the functionality of UPHClean (v1.6) has been incorporated into the User Profile service included with Windows Server 2008 (and Vista too).
However, it looks like a UPHClean 2.0 is in the works which may be made available to Windows Vista and Server 2008 systems. Check it out here: