I ran across an issue this week where one of our customers was reporting that a Terminal Server License error was being thrown when attempting to launch a published XenApp application.  The error stated the following: "The remote session was disconnected because there are no Terminal Server License Servers available to Provide a license."  The odd element of this problem was that this was only occurring  on single machine.  We could never reproduce the error on another computer, and no other users were reporting any issues.

After some investigation a collegue of mine pointed me to following Citrix forum discussion: <a href="http://forums.citrix.com/thread.jspa?threadID=93566" target="_blank">http://forums.citrix.com/thread.jspa?threadID=93566</a>.  To resolve the problem, the effected employee simply removed the Registry subkeys under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSLicensing\Store