Word was unable to compare the documents

[Dave Kennedy]

I have two 147 page Word 2007 documents that I am trying to compare that also
contain equations. When I try to compare them, Word generates the following
error:

Word was unable to compare the documents

I am not really finding anything useful using Google to search so I am
posting here. I did find KB978398, requested the hotfix, and after
installing the hotfix I still have the same error.

Suggestions?

Thanks!