Crosshair Mobo and 4gbs OCZ ram issue

Hi All,

Was just basically hoping for some insight from some of the pros out there ( hopefully with a similar board and ram amount ).

Im running a AMD X2 6000+ at stock, Asus Crosshair Mobo ( bios 0804 - tried all other bois versions too ), 8800 Ultra and 4gbs ( 4x1 dual ) OCZ 8500 ram ( trying to run it at 5,5,5,15 @ 800.

So no OCing or anything. Works hundreds with just one of the dual pairs in the 1st and 3rd slots. Posts, boots and never freezes or CTDs or BSODs etc. Just 100% stable. Ive memtested and physically tested both sets of dimms so i know that they are both fine.

The problem occurs when i try to boot up with all 4gbs of ram in the board. Ive tried all the normal suggestions like upping the voltage to 2.1 from the 1.8 default as well as slightly increasing the CPU vcore.
It just either POSTs and freezes/crashes randomly after varying amounts of time or usually just fails to POST.

So, im just wondering if there isnt some setting i should enable/disable or maybe there is some value for a setting that i should increase due to now having 4gbs of ram as apposed to 2 etc??

Thanks a bunch in advance.