What I do is this:
Close all chat windows and set friends list on offline (and log on to windows live messenger)
That way I only get that bug once/hour. If it still happens just resize your the 4 windows, minimize->maximize the hammer window or something like that.
I get this sometimes, but when I click on something, it usually goes away
Edit: I just had another problem that I've never had before, while looking through the model browser all of a sudden It zoomed in on the top left corner of the browser, every other screen was fine, I didn't press anything and after a few seconds, it went back without me touching it. HELP US VALVE!!!