Log out -
Do a Stop-A - this takes you to the OK prompt.
reset -all - at the ok prompt
This will resync your video card to your pnp monitor, and should solve your problems. (reset -r) could work as well, but reset -all will do it.
Make sure you log out first, and no one is logged into your workstation, since this is in effect a reboot, resync, flush, etc.
But