A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Same problem. Simply closed all Office programs and ran a "Repair" via Control Panel/ programs and features.
Resolved the issue.
My original install was done with Office 2007 still on the computer. I expected the 2013 install to remove/replace the 2007 version but it did not. There was no information suggesting that is the correct order to do this upgrade.
Glad I could find this page for the solution, but when it is that easy to find, it means a LOT of users had this problem.
Hint - Microsoft needs to read these once in a while and issue updates to resolve comment problems.