PC Won't boot with new RAM

I'm having some trouble booting my computer after installing my new RAM, (Corsair VS4GBKIT800D2 PC2-6400 4GB 2X2GB DDR2-800 240PIN DIMM Dual Channel) using W7 Ultimate 64-bit. It goes through normal procedures until getting to "Starting Windows", where it either BSODs or restarts the computer in an endless loop.

This is my motherboard: Gigabyte GA-945GCM-S2C mATX LGA775 954GC. I've checked out the Gigabyte site, and they definitely indicate that the mobo is expandable to 4GB.

I've put my old 2X1GB of OCZ RAM (also dual channel pc2-6400 ddr2-800MHz) back in, and she booted fine.

I've tried booting my PC with just one of the 2GB sticks at a time (tried both) and the same thing happens. Both fail.

I ran memtest86 overnight and it returned 200,000+ errors.. but, it seems like, since it's very unlikely that both sticks of RAM are bad, it's my problem. I haven't really been able to find many/any RAM settings in my BIOS. I can see that the 4GB is running at 667MHz, as was my old RAM. Could this be a PSU failure? Wouldn't it just not turn on at all?

PC Specs:

- Intel Core 2 Duo E8400 Dual Core Processor LGA775 3.0GHZ Wolfdale 1333FSB 6MB
- 3DFUZION GeForce 7600 GT OC SIN Edition PCI-E 256MB 128BIT GDDR3 Dual DVI-I
- NZXT Trinity ATX Tower Case 5X5.25 1X3.5 4X3.5INT ATX2.0 (400W PSU)
- Corsair VS4GBKIT800D2 PC2-6400 4GB 2X2GB DDR2-800 240PIN DIMM Dual Channel
- Seagate Barracuda 7200.9 160GB SATA2 7200RPM 8MB 11MS NCQ RoHS Hard Drive
- Seagate Barracuda 7200.11 1500GB 1.5TB SATA2 7200RPM 32MB Cache NCQ 3.5IN Hard Drive OEM
- Samsung SH-W162 16X DVD+-RW 5X Dual Layer DVD Writer
- Running W7 Ultimate, 64-bit

I'm really not even sure what to try here. I'd really appreciate some advice.

With only the old memory installed, visit RAM Memory Upgrade: Dell, Mac, Apple, HP, Compaq. USB drives, flash cards, SSD at Crucial.com and do a scan. This might provide the needed help.