Hi!
> This past weekend I finally got a hance to try MacBSD again.  I saw
> exactly these same symptoms.
I identified my problem as a combination of the bug reported in the
KNOWN-BUGS file and a corrupted file in /etc (/etc/termcap, I think),
which made the clearing impossible but vanished after reinstalling the
etc10 package.
Thanks again to all who helped me.
Don't know about your specific problem or of the video card you work
with.
Bernd.