Excel 2007 : Track changes

I have an excel file that contains 12 sheets (Jan-Dec). I selected all sheets and clicked on track changes, saved and closed. I opened the file back up and "unchecked" the previous selections I make to track changes, saved and closed. I opened the file again and it appears there is a something over (black background) all of the worksheets except Dec. You can see the row numbers but cannot see the column letters. You cannot click on anywhere except the row #'s. Any ideas on how what happened and how to restore the information?