I have that problem ever so often, but I always clear it up by just restarting my computer. You said you restarted, but did you mean the computer? If you did, then I suspect that your workbook has been corrupted. If you have Excel always create a backup when you save the workbook, then seek out the backup copy and see if you can use it. Incidentally, if you don't have Excel creating backup copies every time you save, then do so on all your workbooks. If you don't know how, then when in a workbook click the FILE tab, then select SAVE AS, then use the same workbook name (no change), but before actually saving it, look at the options. In that window should be a checkbox that you can use to "ALWAYS CREATE A BACKUP".