What OS version do you have and which version of our game are you running?
Viewing post in After hitting Windows key, killing process necessary
With 1.0.3 the problem persists. Only difference is that the look of the mouse cursor stays like ingame. After killing the process via keyboard and taskmanager, the mouse cursor changes to normal and I can use it again.
(Forgot to test the parameter, is it helpful, then I download and install again?)