I would recommend copying the worksheet tabs to a new workbook. Save it under a different name and see if the problem continues. If it does, then try to do one tab at a time and isolate which sheet is causing the problem.
Your MS Office application particularly MS Excel has probably encountered corrupted files or data. This corruption could have many reasons and the best thing you can do is to reinstall your copy of MS Office software and try using MS Excel again and see if it would work.