(first of all, excuse my broken english...)
I had the same kind of problem, with my "home-made" Ubuntu-studio, based on Ubuntu 11.04 (32 bit).
In my case, the problem was with the Pulseaudio server, wich didn't connect with jack, and thus prevented it to start.
I've found two solutions, one was to use another sound server than Pulseaudio. But in that case, I've read that quite a lot of soft's I use wouldn't work any more "as it". So I didn't try it.
The other solution works perfectly on my laptop: a script (written by a nice guy called Samuel) that links Pulseaudio and Jack. But I do not use RT kernel, and I don't know if it works well with RT kernels.
You will find some more explanations in french on : http://www.linuxmao.org/tikiwiki/tik...ght=pulseaudio
Here we are:
Create a new directory, for exemple: /home/your_user_name/scripts . Create (with gedit, kedit, ...) a new file named: jack_startup .
Write in the following lines:
#load pulseaudio jack modules
pactl load-module module-jack-sink
pactl load-module module-jack-source
echo "set-default-sink jack_out" | pacmd
echo "set-default-source jack_in" | pacmd
Save, close, and right click on it. In Properties, authorise it to be "executable".
Then launch qjackctl, and in Settings, Options,
authorise to execute the script after lauching:
In the parameters tab, put a timeout between 1000 and 5000 ms.
Start jack (with qjackctl), and you should see Pulseaudio linked in the Connections tab.
Works nicely with me.
Hope it will help you!