I'm going to throw this out there because it happened to me on a couple of occasions.
I have seen where clicking on the wbar can cause the bar to disappear until next reboot instead of the expected refresh. one time this was a beta version of tc the other I can't recollect. Weird things can happen with the display of windows too, like for example clicking on or near the window handle can cause the window to resize and partially disappear off screen.. Well, I haven't seen either of these issues in a while so maybe it's a moot point.