Your pain is my pain. I have been experiencing a similar issue. I have basically built 2 completely seperate computers using the same Thermaltake Armor+ case and experienced the same issue. I started off with something more like your system, intel quad core extreme processor, asus striker II extreme mb, 4 gb ddr3 ram corsiar (swapped for kingston after freezing began, didnt help), bfg 9800x2 graphics card, 850watt thermaltake power suppy, 300gb velociraptor drive and 1tb green drive.
Worked fine for about 2 months then started freezing during games, then it progressively got worse over the following month to the point that it would freeze before it would even post sometimes. I checked all the settings and components I could and eventually parted it out. I then switched to using a HP low profile computer for 9 months that I upgraded with 8GB of ddr2 ram and a 9500gt card to tide me over.
I decided to try again and built a new system using the case and hds, i got a gigabyte amd mb and a phenom II 720, used the same 8gb of ddr2 ram and the same 9500gt card and a corsair 450w ps. It worked for 3 weeks and then started experiencing the same freezing issue again. After a few times of the system freezing right after launching my game, I pulled the hds, ram and video card and put them back in the HP low profile computer and it has been working without issue, I didnt even need to reinstall the OS switching back from the AMD system to the Intel.
This tells me that the hds, ram, video card, OS (vista ultimate 64 btw) are not the issue. The cpus, mbs and psu are completely different in the 2 builds yet experienced the exact same issue.
Also I had a friend who is an electrician check my power source to the computer and there did not appear to be an issue, but he doesnt know computers so he might not know what would be unacceptable to the hardware.
Anyways, I am left wondering, how can the Thermaltake case be causing the issue? Misconfigured pins? Bad grounding? Has something else been overlooked? Taking this far fetched approach might lead to the solution to both our porblems.