To answer my own question, this works, but it does reset everything and it appears you must then reinstall MusicCabinet:
viewtopic.php?t=1175&highlight=reset+passwordEDIT: Actually, let me reopen this question. It seems like I just have a normal install of subsonic now. How would I get MC back?
EDIT2: Did a purge on subsonic, then reinstalled from the .deb and replaced the files in /usr/share/subsonic with the ones from the standalone package from your website, then started the service. Started getting 503 errors. Read on the forums 503 errors were usually corrupted db issues, looked in /var/subsonic and there was no db folder. Stopping and starting subsonic did not repopulate them.
EDIT3: Read the log file and got a bunch of errors stating wrong Java version. Went and looked and I have 1.6 again. Not sure how that happened, since I definitely installed 1.7 and was running MC on this computer before. Will install Java 7 again and report back.
EDIT4: Mystery solved. I upgraded distro from Ubuntu 11.10 to 12.04 a few weeks ago, which disabled my Java 7 PPA.
EDIT5: The saga continues. MusicCabinet is reinstalled now, but it will not accept the password for the user postgres. Reinstalling postgres did not give the opportunity to set a password.
Fixed with: sudo -u postgres psql postgres
# \password postgres
Everything is working now. Sorry for the big post, but I'm going to leave it here just in case someone else runs into this problem. If you feel otherwise, feel free to delete.