I recently downloaded Ardour2, and it appears that JACK cannot run Ardour along with any other media (Rhythmbox, YouTube, Pandora, etc.). The symptoms are as follows:
If Ardour is the first thing I start after booting my machine, it runs just fine, but if I go to play e.g. Rhythmbox, when I tell it to play some audio it just sits there doing nothing. Similarly with online media. If I close Ardour, I still can't play the other media. On the other hand, if I reboot and open the other media before Ardour, now the media plays fine, but when I try to open Ardour it says:
Ardour could not start JACK There are several possible reasons: 1) You requested audio parameters that are not supported.. 2) JACK is running as another user. Please consider the possibilities, and perhaps try different parameters.
Now I can't start Ardour until I reboot again. Suggestion (2) above made me think that I should try running Ardour as root (the only other user on my machine); when I do this, Ardour works, but it immediately breaks all the other media again.
I've checked the JACK setup for both cases (Ardour started first vs. other media started first), and they look to be identical. Stopping and restarting JACK doesn't seem to have any effect.
Info about my system: Debian wheezy; JACK version: jackdmp 1.9.9; Ardour version: 2.8.14