I've lost the playback sound in Audition!

Hi all,

I am relatively new to Audition but was getting on well - until tonight when my playback sound disappeared. I am editing a multitrack where I am cutting, aligning and muting various instrumental tracks to create a good multiplayer sound. I had finished one section and wanted to hear how the whole thing was sounding, but all the levels were really high causing my headphone sound to distort. So I opened the "mixer" window and lowered the overall output level a little. When I went to play again - no sound! I have checked in the forums here and done a general internet search - the two suggestions seem to be to check that the output device is set correctly - it is - and to check the channel mapping is correct - it is too. It is very possible a rookie error where I have accidentally changed a setting or selected a mute somewhere. Does anyone have any suggestions of what I might have done and how to fix it?   Please?? 🙂 Thanks.