I've got two Canon SL1 with 1.0.0 firmware hooked up via USB to a PC, and am using gphoto2 to control them from that PC. Specifically:
Camera 1 -> Unpowered USB 2.0 Hub -> 15' USB 2.0 Extension Cable -> PC Camera 2
In that configuration, after a few minutes to a couple of hours the cameras are freezing up, by which I mean that the power switch doesn't do anything. I have to remove power (I'm using AC adapters, not batteries) and reconnect it before they come to life again.
Last night I tried connecting one camera directly to the PC, and leaving the other connected via the hub. Now they stayed on for around 4 hours, turning off within about 15 minutes of each other. There was one improvement: now I could get them back to life by turning the power switch off and on, I didn't have to unplug them from power (though I did disconnect USB first for the one directly connected to the PC). I'm going to try working with just one camera directly connected next to see if I can narrow down the problematic arrangement.
Looking around the web I find various mentions of Canon cameras, including the SL1, freezing like this where the power has to be removed. Unfortunately the closest to a cure seems to be upgrading the firmware (which I plan to do), though the release notes don't indicate that 1.0.1 is supposed to fix this kind of problem.
So, I'm hoping my fellow Canon customers will have some advice on either narrowing down or avoiding the problem, or the best way to approach Canon about a problem such as this (I've not yet requested official support).