Insert Columns mystery

"Cannot shift objects off sheet"

Have a large spreadsheet with multiple worksheet tabs, copied from the left. Operations involve lots of cutting & pasting from the "mother" sheet to "daughter" sheets, thus inserting columns, etc. Half of the files have somehow decided they don't accept column inserts?
< error message reads:> "Cannot shift objects off sheet". No insert of course.

What gives? Any experience with this weird error before?