scook - yup, that did it for me! For all of you that bought the wrong encoder option -
like me - find your "Cleverbridge" purchase ID and get a refund - then use scook's link to get the right one.
Some answers elsewhere said don't export as MP3, do a riff, .wav, etc. - then encode with 'whatever'. If you have a .CWP saved with audio data, better than a .wav, etc - it's editable. An MP3 is the last stop on the train - not meant for re-editing.
Forget all the other non-answers, scook's link solved the dilemma for me.