As stated in the title, I have a client running Excel 2013 with some workbooks, she's noticed that when modifying a cell (adding a value, border, fill, or any sort of style), nothing shows up. The cell appears to remain unchanged until she saves her file and then reopens it, at which point cell values and styles become visible. I understand this doesn't happen with every workbook, but a considerable number of them. She first noticed the issue happening on the 19th of November. She's running Windows 7 Professional 64-bit, her Office architecture is 32-bit.
Any help would be greatly appreciated