BSOD no desktop

i turned on my computer last night to the lovely BSOD and ''page fault in nonpaged area''. i reboot and windows asks if i want to repair,i say yes and it gets to a point where i can do a restore to an earlier time. restore goes fine and i proceed to play BF3 for 3 hours with no problems. my son turns on computer today and im getting the same BSOD error,system repair/restore no longer works. things i tried:reseating memory and trying in different slots,clearing CMOS,default BIOS settings,unplugged everything that was not vital,even swapped my AMD video card with an Nvidia based card,windows ran its memory test BUT i can not get to the desktop to view the test results,cant get to desktop at all. tried safe-mode but the keys(f8 and f5) didnt get me there.anyone know how to acces safe-mode on the sabertooth 990fx,i know some manufacturer's have different keys to acces safe-mode. im thinking its the memory but i will have to go buy some to find out.please advise!