Mac Client game sounds muted after patch 6.21

After playing any game mode, sound is muted after the victory/defeat screen. Has also muted itself on loading. Sound returns after client is restarted. Bug has reacquired in my past 5 games. Bug also resets OSX volume to 50% every time.

MacBook Pro (15-inch, Mid 2010) 2.4 GHz Intel Core i5 8 GB 1067 MHz DDR3 Intel HD Graphics 288 MB