Aero not working after memory module failure

Hi everyone, I've been driving myself nuts trying to fix this one, but to no avail. Hopefully someone can help. I built my computer a year ago and installed Windows Vista Ultimate x64, and the Aero feature worked well. Then about three weeks ago I had a memory module fail and haven't seen Aero since. My Windows Experience Index scores are all above 5.0. Nothing else has changed on the computer. When I click on Personalization-> Theme, it is set to "Modified Theme". If I try to set it to Windows Vista I get this error "The visual styles could not be applied." I get the same message if I try to set the color scheme to "Windows Vista Basic" or "Windows Aero". Sometimes the Aero option isn't even there.

Here's what my computer is running:
1) 2 VGA cards Nvidia GForce 6600 and Nvidia GForce 8500GT.
2) Intel Quad-Core Q6600 2.4 Ghz
3) 4 GB of Crucial RAM (Windows Vista does recognize the RAM in the Welcome screen)
4) Seagate 500GB hard drives set up in a RAID config

This computer should be able to handle Aero with no problem. I am a little dismayed that I paid $400 for the Ultimate standalone, and yet Microsoft wants $60 to help troubleshoot. Are they kidding? Why would I pay them that much after I had already been duped once?


Here's what I've tried so far:

1) Updating the Windows Experience Index score.
2) Updating graphics card drivers.
3) Verifying I meet the requirements for starting Aero under Personalization.
4) "Hack" involving registry changes to Composition and Composition Policy (they are set to 1 and 2 like they are supposed to be).
5) Restarting the DWM.
6) Restarting, shutting down the computer,etc.
7) Checked to make sure Vista is actually recognizing the memory.

One thing to note is that I did remove all of the RAM to troubleshoot the problem- inserting the RAM until I found the bad module. I did boot into Windows on 1 GB of RAM, but it is seeing all 4 GB's now.

Any help is appreciated. Thanks.