Graphics problems with MSI Twin Frozr II GTX460 768

Question

Hi,
My previous video card, a BFG 9800 GTX died, so I bought a GTX460 Twin Frozr II 768 and installed it a week ago.  (I also bought 2 more gb of RAM at the same time).  I'm now having several problems with the computer.  My DVD player is no longer recognized for some reason, maybe there's a conflict somewhere?  But the thing directly related to the video card is that whenever I enter a graphics-heavy game such as Dawn of War 2, it works for a few minutes, then everything freezes for about 5 seconds, after which there is massive graphics corruption.  Colors are often inverted to their negatives (blacks become white, for instance), writing is illegible and corrupted, etc.  One time after doing this the computer crashed with an error message stating the NV4 driver.dll had failed.  This happens nearly every time I try to play a game, but there are no apparent problems with web surfing, watching movies, or anything else.
I have searched the web and found many instances of this problem and I've tried many of the solutions, with no success:  I've reinstalled the latest drivers several times, doing clean installs each time.  I've used a Driver Cleaner, even tried doing a Windows System Restore.  I've gone in manually to see if there were duplicate NV4.dlls, which 1 place said is sometimes the problem, and there aren't.  I've run a registry cleaner and tune up program, which another person said fixed his problems, but it didn't help me.  I've even turned down the clock rate and speeds (underclocked from factory settings) the video card by a significant amount, and that didn't help. 
Does anyone have any suggestions?  Do you think it's a hardware problem with the new video card?  If so, should I RMA it to the online retailer I bought it from or MSI directly?  I hate to lose use of my computer again while it is mailed to them and another card is mailed back, though.  I'm not even sure if the card is the problem...
My system:
Core 2 Duo 6600 @ 2400
3 GB of RAM
Windows XP Service Pack 3
850 watt Thermaltake Toughpower PSU

Answer 1

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I took your suggestion and removed the new RAM, and I just tested it.  I was able to play through 2 whole games of Dawn of War 2 and the error didn't happen, so it looks like you guys were right! 
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Core 2 Duo 6600 @ 2400
3 GB of RAM
Windows XP Service Pack 3
850 watt Thermaltake Toughpower PSU
what board you have? Read >>Posting Guide<<
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My old RAM is 2 sticks of 512 Corsair XMS2 gaming RAM, 800mhz, 5-5-5-12 latency.
My new RAM is a single 2gig stick of Kingston HyperX, 800mhz, 5-5-5-15 latency. 
Mixing memory sticks is asking for troubles....No wonder that you have stability issues when you use both of them at the same time
However that's no VGA problem as already proofed.