BleepingComputer.com: Windows Vista Shutdown error - weird and annoying

Where do I begin?

Last July I upgraded to an AMD X2 Processor (waiting for the X4s to lower in price) with 4 GB DDR2 OCZ RAM, and a few weeks after that my system started doing something weird. When I cliked to shut down or sleep, the PC would take forever to shut down, then it would restart and say "Windows has recovered from an unexpected shutdown". It has plagued my system for months, so last week I replaced parts.

I replaced my motherboard, graphics cards and power supply. I reformatted my drive and performed a clean VISTA install. I thought it was working, then alas, its happening again. System takes forever to shutdown, then restarts and gives me the shutdown message.

Before I go Rambo on my case and start replacing everything else, I want to see what someone else thinks. I have figured my problem could be:

1. Bad RAM - 4GB of OCZ DDR2 800 Mhz PC6400 - Was not replaced with the new parts.
2. Bad Hard Drive or improperly configured hard drive - But why would the PC start up fine and work fine if it was a bad drive?
3. Windows Registry - This is a brand new install with barely anything on it, so why would the registry be corrupted the same as before my clean install?

I'm thinking its my memory, but I need confirmation.

My System Specs:

Motherboard: GIGABYTE GA-MA785GM-US2H AM2+
Processor: AMD Athlon X2 2.7 Ghz Black Edition
RAM: OCZ Vista Upgrade Edition 800 Mhz DDR2 PC6400
Hard Drive: Seagate 500GB SATA Drive
Graphics: BFG NVidia 9800GT 1GB
Sound: On Board
Power Supply: ULTRA X4 750W ATX
OS: Windows Vista Ultimate

Any thoughts?

How many sticks of ram do you have?

I have 2 sticks 4GB in total (2 x 2GB)

ok take one out and start and then see if you can duplicate the problem if you can, do this again with the other stick to see if it does it again and then post you findings.