Users may have noticed that it has been troublesome getting jack to start with a card already used by pulseaudio.
The latest pulseaudio update straightens that problem out. Enjoy!
This is the bug report: https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1163638
The bug was not affecting the 13.04 release, as pulseaudio 3.0 already contains that fix.