Need help with video corruption problem

Set up XBMC Eden a while back and keep on hitting this random video corruption problem during play back. Basically from time to time the screen will be corrupted (a lot of big block artifact) which last anywhere from 2-10 seconds.

Problem is not reproducible. Same video will be fine the next time you play it; Some time the problem will be gone for weeks than pop right back up. Not restricted to one kind of codec or resolution h264, RMVB, 1080, 720, SD ... all have the same issues.

It is very annoying because I could run the box error free for days and this issue will pop up out from nowhere.

I ran extensive, memtest86+, Prime95, Fury and video memory test and all came back negative. Switch from a ATI to a Nvidia card wont help either. I suspect this is a codec problem because MPC player and Media Center never have this issues. Also have played with share memory card memory setting and wont help. Really running out of ideas, any suggestion in how to capture the issues or suggestion in how to fix it?

System setup: AMD Phenom X4 with 3G of RAM, Windows 7 32bits, Nvidia GT250 2G VRAM.

Will provide additional information....

Thanks in advance.