Tightrope Not Playing MPG 4 Video File

Hi my name's Kevin Bechet and I work for Woburn Public Access Television. And we use Tightrope to schedule and playback Media. Usually I capture DVD's through the Cablecast DVD Importer, which converts files to MPEG II. Our DVD Cablecast Importer has been freezing up Tightrope recently. So I used a Video Transcoder device to Transcode my Media to MPEG 4, then I draged and dropped my media to my playback server. When I scheduled my program to air it played back black. I know the file works because I previewed the file before I stored it in playback. Any ideas, please help.

Best,
Kevin M. Bechet
Woburn Public Media Center
wpmckevin@comcast.net
781-937-8210 x203