Motherboard Problems Need Help

Not sure if I put this in the wrong forum before...sorry if I did and for double post.

I've had a rough time with this board and I really need suggestions from you guys to try to pick out the best Course of Action. I bought a XFX LT SLi 680i board before and everything worked fine with it for a while until I started getting random BSOD's, lockups, etc. I memtest'd the board and I got errors at the "Changing Inversions" step(or something like that) near the beginning of memtest. Memtest would always crash and give an error report at 21% of that step.

I removed my ram sticks one by one but it kept getting errors at the same point. I tried my previous comp's ram and I got the same error at the same point. It was then that I assumed it might be the gfx card causing issues so I bought a bfg 8800gt oc2 but the problems remained.

I RMA'd the board to XFX and they said the problem was with the board's memory modules and gave me a 780i in return. I was pretty happy about this, however after plugging in all the connections as it was on my previous machine, I tested it with memtest and I got the same errors, at the same step, and the same % (20% actually now) as I had gotten months before. So now, I'm pretty stumped about what to do. Also, I'm not sure if it matters but I didnt format my drives or start over after getting the new board, it went through normally as it was on my previous board.

My setup is:
2 Crucial Ballistix 1GB (2 x 512MB) 240-Pin DDR2 SDRAM DDR2 667 (PC2 5300) Dual Channel kit Desktop Memory Model BL2KIT6464AA663
Intel Core 2 Duo E6850 Conroe 3.0GHz LGA 775 65W Dual-Core Processor Model BX80557E6850
OCZ GameXStream OCZ700GXSSLI ATX12V 700W Power Supply
BFG 8800gt OC2 512MB
I wasn't given a specific model when they sent the replacement 780i. But I know its a 780i LT Sli.

Thanks in advance for any advice that can be given. Take care!