ram breaking stuff *ddr2 pc-6400u*

[star_weaver]

upgraded board cpu and what not, everything works fine untill i put my last 2gb stick of 6400U ram in, then everything just goes to hell, system wont post, no beep code and i need to do a reset of bios and swap around the ram and start with only 1 stick to even get it to post again with no settings done to the bios, no overclock or anything

board: http://www.gigabyte.com/products/product-page.aspx?pid=2543#ov

bios: F13
 

cpu: q9500

all the ram worked fine together in the oem system and all running at 800mhz | pc-6400
am i doing something wrong?