i actually have 33A on the single 12V rail.
my machine isn't locking up and freezing.
the system works perfectly fine. it just doesn't shut down completely.
there are no issues with the machine. it will restart when i hit restart. but when i hit shutdown. it goes through the shutdown procedure, and gets to the part where a normal computer will turn off after the complete shutdown, but mine will just stay at the black screen. the video card has been shut down, i know this because the monitor will receive no signal.
I'm assuming your machine was shutting down correctly before you added the 4850? Do you have another PCI-E card to confirm this?