A family of Microsoft word processing software products for creating web, email, and print documents.
See the following KnowledgeBase Article:
"How to troubleshoot damaged documents in Word 2007 and in Word 2010" at:
http://support.microsoft.com/default.aspx/kb/918429?p=1
The procedure for Office 365\Word 2013 would be the same as for Word 2010.
If that does not help, if you send me one of the documents, I will check to see if it is the document itself or perhaps something else on your system.