i had this issue too but i didn't trace down the cause (not sure if it was pulseaudio crashing) but a few symptoms:
1) phone call - no incoming audio, no outgoing audio. i couldn't hear the other party and neither could they hear me.
2) no audio whatsoever from any app / game
3) the volume slider button would default to the left most position (mute) but you could slide it to the right. sliding it didn't have any effect on sound.
4) a reboot fixed it but the problem would reoccur. usually it seems to be triggered by a bluetooth connection.

i got fedup and ended up flashing to PR 1.3 using USB and that fixed the problem. i didn't bother to troubleshoot much. i think mine was caused by the preenv package?? because the problem started after i installed it. removing it didn't help.