We have tried both of your ideas, however:
1- on the setup window, we do not have a date coumn, and have only 17 columns, in all other sets of books, we have 18 columns
2- we have verified the view sorted by index, and that is OK
We have copied the error- we are not able to paste to the forum, so will send you in an email. Version 2.20 is on this set of books.
Thanks for your help Martin