Game Freeze and loud squeel from speakers

Hello all,

First I would like to say that this forum rocks and has helped me a ton! I wish I had the knowledge to give back on here but I really wouldn't be as much help as you all! I wasn't sure where to ask this question so I apologize if I posted this in the wrong place. Plese chalk it up to my noobness.

I recently updated my old 8800 gtx to a galaxy 580. I know with my mobo, it is not close to an ideal pairing but I was told to upgrade my video card before the rest of my rig (that will happen in a couple months).

I inspected the card and everything looked good out of the box so I went ahead and installed it, plugging in the 8 pin and 6 pin power connector.

Upon boot up, I mean right after she powers up, I get a soft whining noise that goes away after a few seconds coming from the PC. I chalk that up to the galaxy's after market cooler making some noise while getting broken in, but now I'm not so sure.

So I start playing BF3, messing with the settings and I put the AA setting to 16x for kicks. Restart the game and play for about 2 mins and the game freezes and then gets a horrible screeching sound (not the same type you get with sound card problems), and the graphics become blurred. I did a hard reset and brought the AA setting down in BF3 and no problems after that with about 40 mins of gaming. So I try Assassins Creed BH and play for about an hour and it freezes (no screech or graphic blur) but have to do a hard reset. I am not sure if I got a bad card or if it the OC on my chip, heck maybe even memory!

My question to you all is even with the really poor pairing of mobo/cpu to gpu, are these kinds of problems expected? Should I back off the OC on my card because its drawing to much power away from the GPU? I know my pci-e is only 1.0, but a gpu that is 2.0 should be backwards compatible right?

I do have my cpu OC'ed to 3.3ghz keeping a 1:1 ratio with the rest as follows:

MP: 9
CPU V: 1.275
MEM V: AUTO
NB: 1.5
SB: 1.5
FSB VTT%: 20%
C1E, Spread, HPET etc.: ALL OFF!

I never had any crashes like that with my 8800gtx so I am a little baffled as to what this could be. So I am all ears

Specs:
Chip:Q6600 G0 @3.3
RAM:4 gig DDR 800 ram (generic, but it has worked so far)
MoBo: MSI P6N SLI Platinum
HDD: SATA HDD (WD)
Case: HAF 932
PSU: Corsair HX850
GPU: Galaxy GTX 580 w/arctic freezer cooler.

ive had same problem with 6850 doesnt appen often . i think its just on bf3 is .happens. try other game see wot happens