I am trying AVG Free as well. It has already scanned the registry,
processes and system directory and found nothing.
I am doubting a virus, since even pressing Alt+Tab to change between
programs temporarily fixes the issue. I am thinking it is some sort of
mapping problem. I think that the OS sometimes thinks that the taskbar
is offset somewhere.
This advice looked good.
It recommends creating a new Admin user account and using that instead.
The new user account did not SEEM to have the problem (it is
intermittent so it is difficult to say)
But before I could copy my old user profile
'Microsoft Corporation' (http://tinyurl.com/gq9fb
wholesale to see if the bug comes with the copy, the taskbar became
Somehow the new account seems to be faster. Maybe I will stick with it.