I've been playing Super Meat Boy successfully on my iMac for a week, now. OSx 10.6.8. I installed it at home on my PC as well, but this is related to the iMac. I've had no issues until today, suddenly, whenever I try to launch the game, my laptop slows down, a blank white window appears, the cursor turns into the whirling rainbow circle, and after a few minutes, I get a message saying the game shut down unexpectedly.
I've tried verifying the game's cache, as well as uninstalling and reinstalling. I've tried using the launch options to force the game to open in fullscreen, as it was windowed before. No dice.