I had a perusal through console, but faced with a wall of data, even in and around the event, I decided to go and see a genius
at an Apple store who might cut through the confusion. However, after much faffing around announced that it seemed to be a user account problem and that I should do a back up and then do an erase/restore of the whole OS! As I'm the only user and there was no and seems to be no problem otherwise it is all a bit strange to be honest. It's so rare that I ever had a software problem I find myself being somewhat annoyed...
SHJ