Trouble OCing HD4850- Please help!!

So, I recently picked up an HD 4850.... It seems the average OC for this card is anywhere from 690/1050-725/1150 on stock cooling. I haven't been able to get even the smallest stable OC, even though I haven't seen temps reach even 60 Celsius, even under load.. I'm basically limited to 650/1050, though I still sometimes get the VPU recover @ these clocks... The only true stable clocks seem to be 625/993 (default)

I'm 99% sure there is some other problem with my setup, other than the card. I've flashed the BIOS voltages up to 1.158(I set all voltages for 2d/3d to this amount), which is the max soft-increase for this card. The only thing I can think that might be the problem is a software problem, or a PSU problem.

I've also used drivercleaner, reinstalled 8.11 Catalyst drivers after the flash, have my fan turned up manually to 100% at all times...

Below are my system specs.

Motherboard: Gigabyte GA-P35-DS3L
CPU: Intel E2220 Dual core OC'd @ 3.1
RAM: 2 x 2GB DDR2 800
GPU: Visiontek HD 4850 (currently stock clocks but this is the problem)
HD: 300GB basic HD.
PSU- 450W, not sure of the manufacturer/details (I can get them if this may be an issue)

also, 4-5 case fans and a few LED case lights


Looking for any advice on how to up these clocks... Can't figure out what the problem is, I know this card has a lot of potential.

I just get the horrid Black screen for a second, followed by a VPU recovery.. If I disable the VPU recovery, i get the blue screen of death.

The PSU is most likely the limiting factory, your probably teetering on the edge with the PSU then once you OC kablooehy it all goes to hell.