i had the same problem but i had a QX6800 i could get to 3.8 stable but trying to hit 4 it would become unstable. i wasnt able to fix this problem. how are you temps during load? have you tryed moving the cpu glt anymore then just 30+ i know i had a diff cpu but i had mine at i think 40+ is the next step up (i dont have my s2f anymore) maybe moving your multi to 9? what type of cooling are u using?