I have a fairly large (10,000 kb) spreadsheet with 20 tabs. I've been using it for years and save a backup copy every night. When I opened the spreadsheet today, the formatting of many of the columns on about half of the tabs had been changed (different colors, column width, currency to date, etc.). I did not make these changes and I almost never access some of the tabs that were changed. Both the main file and backup had the same changes. Any insight would be appreciated.