Did a lot of messing with this project and tried everything that has been mentioned by both ski and fisherking - thank you both, as 3 heads are definitely better than 1, and ski, I now appreciate what you said about updating - I really had no obvious reason to do so other than to shake up my peaceful little world! Well, nothing worked, I couldn't even get one track to make it to the end even with deleting the other 2. New project - import audio files - nope. No plugs, no input on any tracks, muting - nothing made a difference - so bizarre!
Out of answers.......so, move the file folder to a "different drive" , open the project from the new drive and all is well!!! WTF - I'll never know, nor do I care why at this point - but why does every other project on the initial drive load and run properly with the exception of this one - the only difference being, as far as I can tell, it was the last project started under 9.1.5. Oops gotta go - time for lots of wine
Thanks all
P.S. while a solution has been found, maybe someone can still chime in to offer a better understanding of what happened