My video card makes my monitor flicker black

Hi. Ok, here's what's going on with my computer. Originally, I had a CRT monitor hooked up via the VGA port on my graphics card. Everything worked fine. Then I just bought an LCD monitor, a Samsung SyncMaster 731B, with a DVI input. I tried to hook up the DVI to my graphics card, a Gigabyte Radeon X700 Pro 256MB PCI-E, and when I would boot up my computer, the POST would run fine, but when I got to my desktop, the screen would flicker from black to the desktop; black to desktop; on and on. I finally figured out that my cheapo power supply did not have a 24-pin motherboard connector; it only had a 20-pin, so my PCI-E graphics card wasn't getting enough power to do the DVI output I think. So I went and bought a new Antec Truepower II 550 watt power supply with a 24-pin motherboard connector, and my monitor works via DVI for my desktop and any routine, not heavy workloads. Then I try to play Battlefield 2 and the same problems arise with the monitor flickering to black and then going back to the game, flickering to black and then back to game and so on. When I stop playing, the flickering stops. Why is this happening? And what can I do to stop the flickering? I just spent 80 dollars on the power supply that has more than enough power for my computer or so I thought. Here are my specs if they help any: AMD Athlon 64 3200+, Gigabyte GA-K8N Ultra-9 mobo, 1 GB Corsair Valueselect DDR 400 Dual Channel, WD SATAII 160 GB Hard Drive, Gigabyte Radeon X700 Pro 256MB PCI-E video card, and the Samsung SyncMaster 731B LCD monitor. Any help at all would be greatly appreciated. Thanks.

 

Does anyone at least know or could take a guess as to why my monitor flickers? I know its not the monitor because I have tested it on different computers and it works. Is my video card just designed poorly, or is my mother board crappy and not allowing enough power to the video card? I don't think anything is overheating; I stuck my hand in my case and touched the video card and it wasn't too hot. Thanks!