Sound Playback

I downloaded 2.0 a couple of months ago when my MacBook Pro was still running on the previous OS. Since then I had composed several pieces and never had a single issue with the new version. However, I recently updated to Yosemite and ever since then (randomly) when I open MuseScore and try to play back scores I hear no sound. I try opening and closing the program but nothing works, until it "decides" to on its own (after about 12 hours of not using the program). Or worse, when I open the program a terrible loud, crackling noise (similar to white noise, but more violent) will sound, and I immediately have to shut down the program (for fear of ruining my speakers). I've tried reinstalling MuseScore 1.3 but cannot open any scores that were composed on 2.0 due to compatibility issues.