The issue seems to be have been related to the low resolution MP3 encoding, despite selecting "high" quality on the slider bar - whenever encoding this particular song at 192 (or whatever the default resolution was) it sounded like crap, which never happened before on other tunes, which were louder and far more complex. 

Once I selected a higher resolution using variable bit encoding, it sounded fine, although now I have 10-15Mb mp3 files, but it sounds better. 

Very strange why that happened on this tune only.. but mystery solved.  Thanks all for the assistance.

Karma - looks like you have a budding engineer there in your profile pic - they get bigger if you water them, 

Bob Bone

Hi Bob.. yes.. she's awesome.. and growing bigger all the time.  I'll have to update that picture...