Random screen freezing

I just upgraded from 10.6.2 to 10.6.7 following the step by step. Everything works great except once in a while my screen will freeze and I can only move the mouse around, I then cant click on anything. The computer still is working though when this happens, the only choice I have is to reset it. Any one else experience this? It did not do this when i was using 10.6.2. My GFX was installed using OSX86 Tools using custom GFX string. I hope the 10.6.8 update will fix this problem.

Snow Leopard Client Server 10.6.2 SSE2/SSE3 Intel AMD by Hazard
MB: Gigabyte GA-MA770-UD3P Rev. 1.0
CPU: AMD Phenom II X2 555 Black Castillo Ed. overclocked to 3.82
Memory: 4GB OCZ Combat 1600 running at 1066Mhz
GPU: EVGA NVIDIA GTS 250 1GHz VGA/DVI/HDMI
HD: Seagate 320GB Sata running one partition GUID Mac extended (journaled)

BIOS is Gigabyte F12 running AHCI

Options selected

Blacknight
Chameleon RC4
AMD patch
VooDooHDA
Realtek R1000
AHCI Port Injector
Legacy Apple RTC
AHCI Sata FIX
USB FIX
About this Mac fix

I have exactly the same problem