Good spot – thanks for the tip.
I also noticed this fixed another little bug in the setup I had (WP 3.4.1, WPAudio 3.1, Firefox 15.0) whereby once a song completed it would not start playing again unless either you played another song first, or manually moved the progress bar back to the start. Until I applied the update above, simply clicking the ‘play’ button again for the same song didn’t do anything.
This is a great little plugin. It’s a shame the developer isn’t actively continuing with it.