See if your monitor has a refresh button. Maybe that will help.

Also, try booting into safe mode, see if they appear then, also.

Has it always been like this or was it recently? Did you install or uninstall something around the same time it startedto happen?

You said the monitor works fine on antoehr system and you get the same problem with a different monitor on your system, sounds like video card.

Does your computer stand on its side, like a tower, or is it flat, like an under the monitor system? If its on its side, try removing then reseating your video card, esp if its agp.