Focusing away from Premiere causes playback crash I've been using Premiere Pro since CS5 and am now using CS6. 

I have always had this odd bug where, if at any point while using Premiere Pro I switched to any other application on my computer (Mac 10.8), coming back to Premiere would result in the playback function not working anywhere and the audio not playing, even while scrubbing. The only way to fix it is to restart the app. I am able to save and everything, so the app isn't completely crashed, only playback functions are affected. 

I can adjust the playhead, but hitting the play button only turns it into a stop button, no playback occurs, and pressing the stop button has no effect whatsoever. And as previously stated, audio doesn't play anytime, not even while scrubbing over the footage. 

I have never heard of this bug anywhere in all of my searching. Does anyone know what might be causing this?
1st, make sure you don't have any equipment or 3rd party programs that interfere with the audio on your computer because, more often than not, it is a problem with that instead of the audio on the computer itself. 

I actually asked a similar question (which is specific to your question) about a third party program messing with Ableton (same as with Premiere).

I also answered a similar question (that got accepted) that covers a lot of things about different audio drivers and sound and the tendencies of both.

Since you have Hear installed, make sure to remove the leftover plugin located in Macintosh HD/Library/Audio/Plug-Ins even if you followed the correct steps to uninstall the app.