jackd - no sound

I'm hoping some sound guru can notice something really silly and simple 
that I've done wrong.

Ubuntu 12.04
jackd
yoshimi (synth software)
a midi controller

In the audio panel, yoshimi is connected to "system"
In the alsa panel, the midi controller is connected to yoshimi

When I press a key, the level shows on the synth software display, but 
no noise comes out of the Logitech headset. Sound is NOT on mute. The 
headset IS selected in the sound panel. Sound IS working on all other 
programs (audacity, firefox, rythmbox etc). There are no speakers on the 
system.

I've tried Qsynth and a virtual keyboard too, but the same problem.

After fiddling with various settings, qjackctl routinely locks up and 
has to be manually killed. I'm not sure if this is related.

I get a lot of errors in the message panel thus:
jackd audiodriver::ProcessGraphasyncmster: process error
but I can't find a google reference that relates to the problem I'm having.


Everything used to work but I haven't used this set up for a few months. 
Could it have anything to do with Pulseaudio?

-- 
David McQuire
0418 310312

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