AMD ath ii x3 Unlock Stability

Problem:
I am having sporadic stability issues with my setup (see below.) Problem is, system works fine at load (have run memtest, Prime95, furmark, sea tools all with no hitch whatsoever) but I get occasional hard freezes right after boot to Windows 7 Ultimate. My athlon ii x3 445 is OC'd to 3.26 with an unlocked L3 cache. I'm thinking that the most likely problem would be an unstable L3 cache at this point, or a busted mobo. Would an unstable L3 cache cause problems in Prime95, though? I've tried giving the cpu a little more juice, only seems to heat it up, with no noticeable stability increase.

Specs:
ASUS M4a88t-m le mobo (BIOS set to 240 fsb, 13.5 mult as was recommended on gskill RAM forums)
G.SKILL Ripjaws DDR3 SDRAM DDR3 1600 model 12800CL9D-8GBXL running at 9-9-9-24
amd athlon ii x3 445 OC'd to 3.26 with unlocked L3 (36C idle 50C load)
EVGA gtx 550 ti
seagate 7200 rpm 1tb barracuda

any suggestions would be much appreciated.