I think this isn't really a bug, but the player doesn't output any duration in the playlist or when the video isn't played yet like shown on this site. It might have to do with the duration-tag missing in myextractXML.php. Also in the admin-area of wordTube, I didn't found a way to define the duration of videos nor mp3s.
Will this be included in an upcoming release of wordTube? Or is there a way to solve this issue with an another method?