Does InDesign launch OK without this plug-in?
In that case there might be an incompatibility with the plug-in and InDesign version. Check with Extensis to see if they have released an update for their plug-in as well.
Else try deleting InDesign preferences and caches and test again (see: http://indesignsecrets.com/rebuilding-indesign-preferences.php)
I had tried that (removing plugin) and loged in and out and restarted with no success.
Deleting prefs and restart did not work.
A restart for the 3rd time (mainly because MBP would not awaken from Sleep Mode) has fixed the problem.
I am sorry but cannot figure if either of your ideas worked or what the problem was.
Thank you for your suggestions.
So pleased it is working now.