I agree with dakota81 this sounds like a bad cable. I have seen this many times.
Remove the cable from the video card and look at the connector pins. Are any of them shorter than the others?
Sometimes the pins get pushed in or broken off.
Try, carefully, pulling the pin up with a needle-nose pliers. If you can't pull it up it is probably broken off.
A monitor repair shop should be able to replace the cable for you if you are not comfortable replacing it yourself.
If you connect and disconnect the monitor often, like at a repair station, get a vga adapter for the cable. It is easier to replace these adapters than to replace a cable.
Hope this helps. Good luck.
John