It's highly unlikely the new PSU is having any negative effect on your PC's operation. Perhaps something got dislocated when you changed PSUs?. You might want to reseat any cards and RAM. Check all cable connections. Make sure the CPU and heatsink are properly seated. Then run a RAM test (from a floppy disk, CD or flash drive), to see if you have memory issues causing the stability problem.
Thanks, I Am doing that now.. Hopefully it fixes it.. I Know The 500w Pixxo PSU Sucked and didnt really understand why this PSU would do this. Thanks for your help!