Sounds like a file association problem. I've come across multiple threads on this on the web.

My fix was to right click on the file, open with, and browse for Word 2010 and check "make this default". that fixed it. Here are two threads from microsoft

http://www.microsoftoffice2010forums...ion/office-2-8

http://www.microsoftoffice2010forums...th-problem-lol

hope this helps