I had that problem too. It was a bit different though. Evertime I tried to create a new group or modify an existant my WLM blocked and I was unable to close. The only way was the Ctrl+Alt+Del like you said.
I search for my posts/thread I made to look for an answer to your problem.
BTW, I see you use 8.1. Have you tried uninstall this version and work with 8.0? Is the problem still there?
Edit: I just searched through all my posts I made but didn't find anything. I start to believe that I mad ethat thread in T&T
. I'm sorry. Maybe you could try 8.0 and hope it gets better then