Yes, I have this same problem.
Running WMS 2012, Wyse E01, LG W2240 and W1946S. Wyse units powered from three Startech 4 port USB 3 PCIe cards.
I have noticed that it happens more fequently when I log into a station as admin (not in maintenance mode) then sign out. Weird.
The major problem I have is getting the screen resolution to change. The local monitor will change to anything, the Wyse powered stations will only display in 1024x768, reguardless what local is set to.
I have contacted Microsoft support. No help. Wyse Support. No help. I've tried every registry hack under the sun. Still locked to 1024x768.
The "Beta drivers" ARE the non-Beta drivers!!! Yeah, I said the same thing!
I have hated DELL all my life, for this reason. They really, REALLY SUCK! At customer support, quality of service, etc, etc.
I really like WMS. 2011 version was good, solid on the E01. 2012 has caused us nothing but grief. I hate to say it, if I can't get over these hurdles, boss looking at a Linux replacement. Licenses are cheaper, and the company that makes it gives 100% support on hardware/software.