This is caused by a security update, details and workarounds on the link below http://www.infoworld.com/article/3098898/microsoft-windows/excel-refusing-to-ope

This is caused by a security update, details and workarounds on the link below http://www.infoworld.com/article/3098898/microsoft-windows/excel-refusing-to-open-files-blame-the-kb-3115322-3115262-security-updates.html http://www.infoworld.com/article/3098898/microsoft-windows/e...