Hello,
Several weeks ago, I mentioned that in a heavy snow things can get wierd
while driving my vanagon.  It turns out that other people have experienced
the same thing.  I think I now have a solution which worked the one time it
was tested. Here it is:
Based upon a comment someone made about the top of the cab helping this
sensation, I found that I can control it and therefore continue driving
safely by lowering the sun visors and turning the instrument lights up to 
their maximum setting.  This worked for me, but I still say that if you
experience this strange sensation, stop driving until it goes away.  It is
completely dangerous.
Stuart Hutton