Has anybody else had issues when playing blast arena?

When I am playing from time to time the audio is gone (all audio from my computer, until I force-quit spiral knights), and a few seconds later the game freezes. (The game only freezes while playing blast arena)

I lost a lot of money because of this, and it is really annoying the hell out of me. Since that update you no longer go back to the arena when I restart the game (and lose your money and even the 1 coin you get for losing). Does someone know how to fix this or at least do something?

I play spiral knight on Steam, and I'm using a mac (iMac), I have already set everything to low, and I still have the problems.