To give more details ... I partitioned my MacPro into Lion and Mountain Lion for training purposes. When I plugged in my iPad2 to the Mountain Lion iTunes - it warned me that iPad 2 could only be synced to one iTunes library (even though it was my same account.) So I hooked it up to the Mountain Lion iTunes - and started from scratch. Later I decided to go back to the Lion iTunes - so re-synced it back up there. That's when iBooks stopped working. I've deleted from iPad/iTunes/forced restart/reinstalled - still crashes when starting up.
Someone suggested that my iPad2 needs to be restored as I may have broken a thread somewhere with all the switching of iTunes accounts. So getting ready to tackle that. Thank goodness for iCloud backup.
Thanks for all your help - still struggling!