Stuck on "Preparing Source"

I’m using a Canon EOS Rebel SL1 (which I know isn’t officially supported, but I have used it without a problem in the past) on a late 2013, 15-inch retina MacBook Pro. Whenever I attempt to select my camera as the source, a drop-down with the phrase “Preparing Source” appears. I’ve contacted Boinx Support, and tried everything on the list they sent me, but nothing seems to work. Anyone have any ideas?