Memory voltage settings to sort out random freezes?

So ok, i just upgraded my rig to the following and having random crashes in games like wow, far cry and sometimes randomly on windows or media player playing a video. It's completely random can be after 5 hrs or 5 mins, nothing Overclocked, everything in factory settings.

So here is my spec:

Asus Striker II - Extreme n790i mobo
Q9650 Quad Core 3.00 ghz processor
3 x 2 GB Corsair CL9 1600 mhz ddr3 memory (9-9-9-24) 1.65V
Seagate barracuda 1.5t sata3 7200rpm
Asus Nvidia 9800gtx (non-sli)
1000w Coolermaster PSU with full tower Coolermaster case(very good internal cooling)
On board sound card
Windows Vista 64 sp1 home edition

All board drivers installed, latest nvidia drivers, completely new build windows, the only item i saved from my old rig was 9800 gtx, never had freezing problems with it so its definitely not the card itself, can be the Nvidia vista64 drivers or compatibility issue with the new mboard or the memory voltage settings in the bios. Checked hard disk and run hdd diagnostics, without any problems. Havent tried memtest yet but planning to..

Did anyone have problems with such a system. Will upgrading my gfx card to 295gtx help? Or setting my memory settings in the bios?

I am completely noob when it comes to memory settings on bios, so which values would i have to do change the settings to match the memory factory settings to minimize the system freezes. The pc performs very well it is, dont need overclocking, i just need to get rid of these freezes. Appreciate your help in advance.

Ta.