OpenAL Soft (the default OpenAL implementation) causes troubles in combination with PulseAudio that is used by default on the Ubuntu desktop. These troubles can be very different going from just no sound to crashes and freezes of apps that use OpenAL (mostly games).
The root cause for this seems to be that OpenAL Soft doesn't use it's new pulse output on systems with pulse running ( http://www.pulseaudio.org/wiki/PerfectSetup#OpenALApplications ) and/or the pulse output is a bit buggy. So instead of using Pulse directly (& correctly) it uses ALSA as it's output and because ALSA also has a pulse plugin the sound is routed to PulseAudio and then back to ALSA. But this seems to be buggy, in Ubuntu at least ;).
I did this new report to synergize all the efforts of the various reports about this issue, so there is already plenty of information on the different troubles and on suggested solutions in the duplicates. That's why we should try to stay focused here.