I had a similar problem a few years ago and it was very frustrating. In the end it was the AGP card, it was not seated properly in the slot. It looked like it was but it wasn't. I would take it out carefuly, re-insert it again, make sure it is all the way in the slot, especialy the end that is near the side of the case. I also agree with Flanzig1 that PSU is way small for your rig.
Good luck.