When I open it, it shows an error message.

[Joe Lawrence]

See screenshot. It says the Jack audio thing failed, but I know I have it. I have Ubuntu 9.04 32-bit.

[Daniel James (daniel-64studio)]

There appears to be a problem with support for libtool being stripped in recent libjack-dev packages from Debian/Ubuntu (after 0.116):

http://packages.debian.org/changelogs/pool/main/j/jack-audio-connection-kit/jack-audio-connection-kit_0.118+svn3796-2/changelog#versionversion0.116.1-3

If you installed jack2 or built jack2 from svn there may be a different bug as well, to do with jack2 not providing /usr/lib/libjack.la upstream, which is hinted at here:

http://lalists.stanford.edu/lau/2009/05/0251.html