I can't be certain, but from having installed PlayIt Live on quite a few different sets of (generally) poor quality hardware problems tend to be sound card related.
In particular, if a USB sound card has any mechanical issues (so becomes "lost" to the PC) I would expect PlayIt LIve to throw a wobbly !
If it does it again and there is a chance (and I appreciate sometimes it's not really practical to investigate) restart the program and see if any sound devices have lost their selection.
If so, has something happened to the related sound card.
We've just had a user who had PlayItLive crash whilst broadcasting.... I've had a look in the windows event logs and it reports the Audio Processor crashed. This is a clean install of PlayItLive installed yesterday.
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.AccessViolationException
at Un4seen.Bass.Bass.BASS_ChannelRemoveFX(Int32, Int32)
I've attached the full bug report.