I have the same problem here when I connect my lcd with a dvi cable. I remember somebody saying that it went away or decreased if you lowered the refresh rate on the monitor. Try 60Hz or somesuch. This is obviously not a fix but it might help.
I can't use the dvi connector because it causes problems with my tv-out and I don't see this problem with a vga cable.
You have to restart X if you change connectors. Reboot the machine to get the console back if you use startx.