Vista - Vista Business Taskbar flashes, is unusable

There are other posts on this subject, but as far as I can tell, they're
unanswered. The problem is that after using Vista for a couple hours on a
computer docked and thereby connected to a flat screen, and often after
coming back from the screen saver, the taskbar flickers, flashes, and the
icons are unusable. So is the Windows button - the result is a shadow where
the list of programs should be. The only resolution is to reboot. I thought
this was a problem with the Dell computer I was using, so I got a new one
(620) with a vastly upgraded video card. I also changed flat screens and
updated the drivers. The problem persists. HELP!!!