I think, that I've posted this before - on casual events my IDE GUI does not response (VA 8.x under W7/64 - but this happened earlier also). The only way is to kill the IDE.
I'm still not able to say, how I managed it - but because this happened more often during the last days I think, that I got an idea, where it comes from. It's the way, how I move my windows around. When I move a window around I very often do not release the left had mouse button (because I read a content in another window). Therefore the moved window, selected slider or whatever I had in focus - remains active selected.
But I still have no repeatable way of producing this problem ....