I find that when dumping from the MPC to my MAC, it WOULD freeze if you're dumping all at once. I find that if you dump CHUNKS at a time you'd have a higher success rate. It may take more time but once you get it done you'll have no worries about back up.
I also tried that BACK UP on the utility page, when it's all said and done it's just an itty bitty file that can't possibly be a back up of all the sh!t i've got in my system.