1) Take out one stick of RAM so only one is in the mobo
2) check the RAM settings in Bios against the recommended settings of your RAM to make sure they match up.
3) If still having problems try with the other stick of RAM
4) If still having issues try playing around with the settings a bit. My RAM recommended setting was 7-7-7-22 and 1.6v. Yet my computer would not run at this setting. When I up'd the voltage to 1.7 it ran but all games crashed.
At 9-9-9-24 (default in my bios) I kept suffering freezes at all random times.
My computer now seems stable at 7-7-7-22 though I had to reduce its speed to 1066mhz.
Having said all that, I have been having issues with windows 7 itself, so now that I have managed to install the windows updates (some were stability updates) I may start to play around with the RAM settings again to see what I can get.