Arthur, I tried that approach anyway. Backed up the plugins folder. Uninstalled the app, Avid link etc., then deleted the files and folders and wavecache files. I didn't delete the preference files (I forgot). Re-downloaded and reinstalled and so far it has not failed. It is still hitting the computer system CPU hard causing the fans to go into overdrive but it wasn't falling over (not yet at least). I am keeping an eye on Pro Tools system usage dialog and so far the track I was mixing was only hitting around 50-55%. Falcon decided to behave too.
I have yet to discover what if there is anything I can do to alleviate the fans going crazy but, like I said, this is my main computer so it could be that.
Thanks for the feedback so far.