I recently builded a new computer. But sience day 1 i have had problems with random freezes and crashes. even when only listening too music my computer can crash!
First i used OCZ PC 8500 RAM witch was not supported by QVL so i tough changeing ram whould do the "magic" trick for me. But NO no no!
My timings: 5-5-5-15 and DDR volt too 2.1 in bios manualy!
Tower: Antec 1200
MB: Asus p5q-E (Newest Bios atm, tryed with 3-4 others too)
CPU: Q9550 with Nocua fan! (Stock speeds)
GFX: Gainward Radeon 4780x2
RAM: Corsair Dominator TWIN2X8500C5DF 4096MB
PSU: OCZ Game Xstream 850W
HD: Old one from my old rig. 500GB
I have done memtest for 6 hours. No errors at all!
my first suggestion would be to reset the BIOS. Use the defaults and check for stability. Also check your temps. Overheating can lead to instabilities so download a couple programs like Asus PC Probe II and Real Temp and check the temps for your CPU and Chipset. You can also download GPUZ and check the temps of your video card.
As for the 8500 RAM and it not being on the QVL. I am using Mushkin DDR2 8500 which isn't on the QVL for my board and it works fine. All the QVL is is a listing of memory that they actually tested and found to work. If you download and run CPUZ and choose the SPD tab you will see several different settings for your RAM. At least one of them will be a JEDEC specification, likely something like 800 5-5-5-18 1.8v. When you reset the BIOS it will set the RAM to one of the JEDEC specs.
I don't think the RAM is your problem but it's possible that there is some kind of conflict there. Also it may be instabilities in the power delivered by your PSU. You have a good PSU but things happen and sometimes good companies make bad units. PC Probe will allow you to look at all your voltages and temps and see if there is a problem somewhere. You never know but a clean install may fix the problem as well. I have had situations where for some reason the OS just didn't install correctly and the system didn't run right but a reinstallation fixed it.
But all it really does is check that power is going to each output. Asus PC Probe allows you to monitor several different voltages and you could look at them at idle and load and look for severe droops or fluctuations. Unfortunately there isn't a cheap way to really trouble check a PSU but there are a few things you can do to look for trouble.