Adobe Audition not playing audio

I upgraded from Cool Edit Pro to Audition 1.5 when it cam out and have used it ever since. I use about 0.015% of it's features but that is all I need. I have been having problems with getting audio ooout of it so  had a new desktop built (previously used laptops both had this problem) and now find I have the samee problem.

I record radio programes fro a local community radio station. I drop pre selected music in to one traack and record the audio in the second then mixdown into  a third track. This mixdown then gets sent to the rssdio station.  However now, although both thee music and the audio appears in the tracks and the audio I record shows, when I play it I get silence.

What am I doing wrong.

alan

AKA Percy