I had this nusance problem for a while.
I have Dell Inspiron 8000 laptop, GeForce2Go.  And using X 4.2.1 date 2
sep 2002

It works ok most of the time except this one situation.
Sometimes when i am in X for a while and want to switch to one of the
other virtual consols the screen freezes and it seems like the machine
is frozen.

I just had this happen again so i ssh into my laptop remotely and X was
out control on the CPU, i was able to kill but Virtual consols display
won't come back.  I could switch to the concol and type commands blind
and things work fine.  Whenever i type something the picture of the
frozen screen would scroll to the left and keep wrapping around the more
i type at the consol, queit funny actualy.

Anyway there is no way to get the consol back but i did restart X and
surprisingly it came back to live although trying to go back to the
virtial consol freezes it again.

felix