KB Article: http://support.microsoft.com/kb/2655998
Consider the followingscenario:
In this scenario, the logon time increases every time that you establish an RD connection. Additionally, the % Privileged Time count increases in the Svchost.exe process that hosts the User-mode Plug-and-Play Service (Umpnpmgr.dll) on the server. This behavior occurs every time that you log on, log off, or reestablish an RD session.This behavior may cause performance issues such as slow boot, slow logon, system hangs, or failure to redirect printers and mapped drives.