I recently built a second machine to use as a home studio/office computer. I'm running an AMD Phenom IIx4 960T (unlocked to 5 cores... the 6th wouldn't let me boot to Windows no matter what Vcore I gave it ) with an ASUS M5A88V-EVO and 2x4GB G.Skill RipjawsX 1600Mhz DDR3 ...using two monitors plugged into the onboard video, was gonna use an old GTX 460 I had laying around, but it had to be RMA'd. I'm also using a Hyper 212 Evo on the CPU

My goal is to get it running at 4 GHz, but right now it seems I'm stuck at 3.9Ghz (I know it's only 100MHz, but dammit it's so close!) Running at 200x19.5 @ 1.45V with the CPU-NB running at 2800MHz (1.325V I think) and the RAM at 1600MHz (had to bump it up to 1.6V when I unlocked the 5th core at stock speeds) it runs perfectly fine... 15 runs of IBT on maximum and 8 hours of Prime 95 showed no errors whatsoever, and temperatures peaked at 56C (this is the CPU temperature in HWmonitor... the individual core temperatures aren't usable with an unlocked processor, so I'm flying semi-blind as far as temperatures go) But when I up the multiplier to 20 to get 4.0GHz, one of two things happens: 1) I get a 0x1A BSOD or 2) The screens freak out and go all wonky (to say they're artifacting would be an understatement) and the machine has to be manually rebooted, which makes me think the onboard video in the chipset is crashing. I've tried running the Vcore up to 1.475V and still it crashes in ~5 minutes of Intel Burn Test on maximum (I haven't tried higher because the CPU temperature hits 60C, and I've read the max is 62C for Phenom II CPUs) which makes me think it isn't the CPU causing the crashes. The 0x1A BSOD seems to point to a Memory Management Error, which means test the RAM for problems... but neither Windows' memory test nor Memtest showed any problems with the RAM.

So, people who are more familiar with overclocking AMD processors... any ideas on what to try, or am I stuck at 3.9Ghz? I've read a few guides on overclocking Phenom II's so I know sort of what I'm doing, but nothing they mentioned seems to be helping with my issue. I know that unlocking the 5th core is limiting my overclocking headroom, but I'm using the PC for audio processing and the extra core should help out more than a few hundred MHz.
(Also, I know... "why AMD?" I wanted to play around with overclocking, and to build a cheap machine... which are two words that don't go together with the Sandy Bridge series unfortunately (wtb i3 2100k )