Taskbar problems.

I have no idea what causes this to happen but every now and then the taskbar
on my machine messes up. The start menu, quicklaunch bar and any windows I
have open are shifted to the extreme left side. But only the -image- of them
is shifted. If I manage to click in the right place I still open the correct
window, I.E., where the window was located before they got displaced. I
discovered I can temporaily fix the problem by terminated explorer.exe and
re-running it with the task manager but would love to find a more permanent
solution to the problem.

Any ideas what may be happening?