Could be a wire/connector issue with the card and/or cable/connector.
I saw a crappy monitor at work that flicks in and out of color when I touch the cable. Once I had a blue screen that has caused by a broken pin (for the red color I suppose).
Check the connection to make sure it's tight. Jiggle the connection point (gently) to see if that helps. If not, then check the pins. If you have a broken pin, you may be able to find d-sub connector at radio shack and re-wire the sucker. It'll help if your manual lists the wire layout.
It could be the gun. It could also be a defective card (some kind of connection defect).
Quality is better than name brand, even regarding beloved AMD.