Ok, there seems to be a bug in jackd or ALSA or PulseAudio. I've been working since yesterday to get it to run and did these:
You need to un-install jackd2 and install jackd1 instead using Synaptic.
Then, install Ardour (686), and remove the Ardour default installation.
Launch QjackCtl and click Setup->Interface to hw:0,0 or default (vice-versa).