AMD Phenom X4 955 build locks up, freezes, or re-boots

Okay, still running into a problem with my system that locks up, freezes, or re-boots.

These are my components:
Cosmos 1000 full-tower case
AMD Phenom II X4 955 BE cpu
Gigabyte MA785GMT-UD2H motherboard
Zerotherm FZ120 heatsink/fan
4GB Obsidian (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)
ATI Radeon 4600 video card with 512MB RAM
Coolermaster 600 power supply
Windows Vista Home Premium
three hard drives
dvd burner

I know it's not a heat issue because I have tried four different heatsinks and tried every method of thermal paste application, from a lot to a little, used the plastic bag method to smooth it out, put a pea sized in the middle of the cpu and squished the heatsink on it like Arctic says to do. I was using Arctic silver 5 by the way. I mean, I can definitely give out advice on what works. I finally went back to what Arctic says about a dab about the size of a bb on the middle of the cpu and then flatten it with the heatsink. Anyway, Core Temp tells me my cpu temp is 35 to 48 Celsius so the temp is not the problem.

I have switched out video cards so that is not the problem.

Is it possible that the cpu I bought was damaged before I bought it? I know cpu's are pretty durable. If that were the case, it should not even work, right?

I am going to give the Arctic 200 hours to set properly but again, cooling is not the problem.

I was thinking about changing the power supply but I don't think that is going to make a difference because the one I have is pretty good a rated well.

Anytime I try to run a processor overbearing program like a video editor, the machine locks up, freezes, or re-boots. It's funny that an older Pentium 4 computer I have will run the same program but a lot slower, without any issues. Just takes a lot longer, hence why I built this machine.

Any advise would be great.