Power supply or game?

I had to rma an EVGA 7900gs that the fan had FROZE in. I was disappointed with the 8600gt they replaced it with. They graciously agreed to send something else. Imagine what a suprise it was when they sent a GTX 285 1GB superclocked edition! EVGA knows how keep customers brand loyal.

The 7900gs was in the wifes rig, so she got the 8800gt out of my main rig. We are both happy.

I ran 3dmark 06 a few times and played Bioshock for hours with no issues.When I registered the GTX 285 I got a free Cryostasis download. Cryostasis keeps locking up the box. It doesn't crash to the desktop, it is completely froze. I can't ctrl, alt, delete, the only way to fix is hit the reset. I keep lowering the settings in game, first I turned the physX down, then off, then lowered the res to 1680 x 1050.

I am wondering if my power supply isn't up to par. I have an Antec Neo 550 and from what I can tell it should be ok. It has 3 virtual rails at 18a each for a combined total of 504 watts. P=IxV or I=P/V so I figure I'm good for 42 amps on 12 volt combined.

I figured I would ask the experts here. When a P.S. balks at a load wouldn't the computer reboot instead of locking up?

My system specs are:

Gigabyte GA-EP45-UD3P
Q6600 GO @ 3.0Ghz 1.3v
Scythe NINJA PLUS Rev.B CPU Cooler
Crucial Ballistix 4GB (2x@GB) DDR2 800 2.0v 4-4-4-12
Antec Neopower 550w Power Supply
EVGA GTX 285 Superclocked Edition 1GB
Western Digital Black WD1001FALS 1TB 7200 RPM 32MB
(2) Samsung F1 Raid class HE103UJ 1TB 7200 RPM 32MB Raid 1
Samsung SH-S203B SATA DL-DVD-RW
Creative X-FI Platinum
Acer X243W 24" LCD 1920 x 1200

Thanks in advance for your advice.