I've not had the problem and I tether to a MacBook Pro and iMac, but I don't push hundreds of images off my cameras during a shoot.
I'd hack at this problem a couple different ways. To simply get the system to lock up, run the software (EOS Utility & Capture One, Bridge or whatever) and also run the Activity Monitor. Float the inspection windows and start shooting tethered. Set the 1Ds3 to small-raw and just fill up the pipeline. The information derived will show what's happening (maybe a buffer or cache overrun?). Send this to Apple & Canon.
Second, for live jobs, shoot the lighting setup tethered (i.e., a digital Polaroid session) and once everything is dialed in, untether and use a card reader. This will allow for fast shooting of unlimited frames.
I know this is a lousy hack, but something is better than nothing. A locked up computer kills all levels of productive workflow.
One of the problems photographers face is that Canon isn't the most nimble software developer on the planet, and Apple is constantly updating the OS. EOS Utility is designed to accommodate all their cameras, too.