Computer Freezes

I hope someone can help me out with this problem. My computer is about a year and a half old. The specs are:

Core 2 Quad Q9550 @ stock speed
asus rampage formula motherboard
4GB Corsair DDR2 1066
nvidia xfx 9800gtx
creative x-fi fata1ity edition (pci not pci express)
2 300gb v.raptors raid0
pc power & cooling 800w psu
Windows 7 Ultimate 64bit

My computer has been freezing up for a month or so now. It only does it when the computer has been on for a while and does it
either while gaming or just idle on the desktop. When it does freeze strange garbled static like sound comes out of the speakers or my headphones. I've checked my temps and everything is running at what it always has. Asus temperature probe tool reports that my north and southbridge are running too hot but i've read differing opinions on how hot these things should be running. does this sound like the problem or could it be sound or graphics card related. any insight someone might have will be greatly appreciated. It was doing other weird things before the freezing started. Sometimes one or both of my optical drives would not appear to be connected and would then reappear after one or more restarts. Then I was getting S.M.A.R.T. errors stating that one or both of my hard drives in my raid0 were faulty. I RMA'd them both, now I have new drives. Then I was running Prime95 and all threads were failing instantly after the torture tests would start. I ran memtest and it said one of my ram sticks was faulty. I replaced it and now I still get the occasional failure in Prime95 as well as the freezing. Keep in mind i'm not overclocking at all. So is this my motherboard, cpu, or something else. Please, any help would be great.


*EDIT: Today when I was checking advanced tools in Windows 7 it says that it has been keeping a log of errors relating to my videocard not having enough memory, which i find hard to believe because although it is not top of the line it more than exceeds the recommended specs for the OS. Also it says their is a problem with my Logitech G19 gaming keyboard, i've uninstalled and reinstalled its drivers several times with the same results. So to me it's starting to sound like maybe my motherboard is to blame for all this. Am I right? Can someone please help me out.

I have a Nvidia XFX 9800GTX(G92) 512MB GDDR3 XXX Edition
core clock: 740mhz
memory clock: 2280mhz

Yes I've run memtest overnight twice just to be sure, with no errors reported. It's also worth mentioning that when I tried to run memtest either from a standalone memtest disc or memtest off of an ubuntu live disc, it would not run unless I set my sata ports to IDE mode rather than the RAID mode they're normally set to. I don't know if that's normal or not, but I thought I should at least add that bit of info.

Yes that's actually something I already did a few days ago after reading another forum post about RAM problems. I appreciate your replies and suggestions.