If the DVI monitor plug is making contact with the case while plugged into the gfx card, would that short something, preventing the monitor from coming on when you shake the mouse to wake it? My monitor wouldn't wake up today, I had to force a shutdown, by holding the power button to get back up. My case is a bit imperfect, so things aren't lined up as neat as they should. I installed a gfx card a few days ago and everything has been fine until today.
Stupid question, I know, but I had a PC a very long time ago that wouldn't allow the monitor to wake because of this.