Sounds to me like a memory issue and not your PSU. Plug in the old PSU outside the case and see what happens just to be sure it isn't that PSU. If all loads well it is time to RMA that power supply. I would go with an Antec Smart Power 2.0 550wt if I were you!!! If yo have the same hang up problem, try pulling the memory and reseating it. If prob persists, run Memtest86 and check taht memory for probs.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.