figuring out what is using hw:0 question

[Kevin Kofler]

Not really an answer to your question, but if you can tolerate some small extra 
latency (at least if your card doesn't support hardware mixing), set up JACK to 
use the "default" device rather than "hw:0", that way it should play nicer with 
other apps (as "default" normally uses either hardware or software ("dmix") 
mixing to allow multiple applications to output sound at the same time). Note 
that you may also have to set the other app up to use "default", hopefully you 
can figure out which it is.

        Kevin Kofler