No sound from one sequence?

I must have missed something simple? I have a sequence from which I cannot hear any sound. Other sequences are ok.

I can see in the audio mixer on that track, that it has sound, but on the audio tool I cannot see anything. all the tracks are turned on. If I place the same music clip into a different sequence, it plays ok. must be something wrong with this sequence, but what?

thanks 

Lembit