Originally Posted by Arup
Can you tell me whats the rating of your PSU? The newer 8400 card will draw more power than your older 6200 so it might be that when the card goes to graphic mode, it fails to draw the requisite current from your PSU.
Yes, I replaced the original Dell PSU with a brand new Corsair 400W unit. According to the Corsair spec, it can deliver up to 30amps on a 12 volt rail, and 20 amps on the 3.3 and 5 volt rails. Was a bugger to fit - I had to hack away some of the rear chassis.
The PNY 8400GS PCI card takes all its power from the PCI connector - there is no other power supply connector on the card.
It could be that the motherboard PCI connector doesn't like to handle the power being consumed by the 8400. When the card goes into graphics mode, maybe the sudden increase in power consumption is too much. The PSU can handle it, but maybe the motherboard can't. Pure speculation from me.