Tuxguitar stopped working after upgrading to Ubuntu 10.10 Alpha. Many people seem to be having this problem after a distribution upgrade.
The fix is simple. Install timidity and tuxguitar-jsa package.
sudo apt-get install timidity tuxguitar-jsa
After the install, run tuxguitar and play a file. You should hear the sound. If you still cannot hear it play, goto Tools->Settings->Sound
In the MIDI Sequencer drop down list, select ‘Real Time Sequencer’. In the MIDI Port field, select ‘Gervill’ and click on Ok. Click on Yes when it asks for confirmation.
Try and play sound again, and you should here it this time.