Ardour startup - cannot connect ardour:auditioner/out 1 ...

I’m using Ardour 0.99.2 on a system with Ubuntu 6.06 and Jack / qjackctrl.
On startup, I permanently get the following message:

cannot connect ardour:auditioner/out 1 (ardour:auditioner/out 1) to ardour:master/in 1 (ardour:master/in 1)

(and the same for channel 2)

Recording via the external USB soundcard (Edirol UA-1x) finally works, configured as “duplex” (in + out) via Jack. Playing back the audio files is displayed on the level meter of the track, but not on the master/out fader meter. I have tested various connections etc. in Jack and Ardour-Track Bus Inspector.

Does anyone have an idea to solve this ? Thanks…