This is a well known problem with the Striker families,I'd suggest you to take one ram stick out leaving just one in (if it's 2x2gb)and try again.
Have you updated your Vista to SP1 yet?
What version of bios is your mobo on?
If that works,fine,if not then you may have to take out one 8800gtx or 2 leaving just one on the primary slot.(The top one nearest to the CPU)
Patience is needed,it took me a month to stablize my system although I have the SIIE with 2x GTX280.