Strange artifacts with new graphics card

So, i had a desktop for about 2 years. Not a bad machine, but not fit for gaming. I upgraded it a lot today, and at first i loved it....and now im upset with it. Its an XFX HD 4890. Aside from that, my computer looks like this

Amd Phenom Quad Core 2.2ghz
6GB DDR2 Ram
550-watt power supply
HD 4890 video
650gb hard drive.

I decided to upgrade the video card and power supply so i could play dragon age. The card required 500 watts, so i had to upgrade to the 550 i have now, up from a 300 watt.

I first tested with world of warcraft, and it ran like a dream on the new 23 inch monitor i have at 1920x1080 (i think thats the resolution). It was at max settings (first time ive ever seen wow run at max settings) and it was amazing. had no problems.

Then i decided to start playing dragon age for awhile. Everything was good for about 30-40 minutes. I then noticed that i was getting some strange artifact, which kinda looked like certain frames getting stretched into a huge flat plane that spread across the entire screen. It started with one. then another, and then before long the screen was nothing but a jarbled mess. I managed to alt-tab out of dragon age after about 40 tries to see that my desktop was almost completely unreadable due to other artifact. I let it sit for about 5 minutes and the screen went black and then came back up, everything normal. It notified me that my video driver had failed, but had recovered.

I tried dragon age again. Same problem, only this time it hit me with a blue screen of death saying that windows had to shut down immediately to prevent harm to the computer. I rebooted and started dragon age again. Same problems. I decided to underclock the GPU and ram slightly, and pushed the fan to 100%. My computer was screaming with all the fans going, and the issues still persisted.

I was checking around the catalyst control center for the card, and noticed that while playing dragon age i was hitting 75+ Degrees Celsius. I tried everything i can, and im not able to fix it. Is this an overheating issue? Can my computer not handle the card? Is the card damaged?