ALSA error with SWEEP
 

Using sweep to edit a wave file. So far am able to load an existing file. When I use the scrubby to make a selection and then play selection I get the error:
error opening ALSA device plughw:0,0:
No such file or directory
Can someone explain this error in terms of ALSA and what is plughw?
Thanks
As an addendum this error does not alway occur as I have successfully cut/pasted some music for use in theatrical performances.