Occasionally, when people login to the terminal server (Standard Server 2003, SP2), they are presented with nothing but a blank screen. This has happened for three users only in a 25-person network. They are logging in from a thin client, but when this happens I login to their profile from a computer (with RDP) and get the same result.
Their session does not appear under Computer Management -> System Tools -> Shared Folders -> Sessions, so I can't just reset the session. If I restart the server, then they can login again, but I don't want to have to do that every time.
The only errors in the event logs related to terminal services are complaints that certain printer drivers are not available.
How can I find out what is causing this problem, and fix it?