Are you saying that the screen just freezes and you cannot do anything with it? Sometimes you have to just shut the machine off and lose whatever changes you have made to whatever project you were working on. When you restart, you will get a message about "improper shutdown", but everything is working again. Is that what is happening? Happens to me all too often.
And this only occurs in a single user profile?
If yes the easiest fix is to just create a new profile and migrate over to that one.Lots of things can corrupt a user profile such as program installations that go wrong or even a virus.