QM file won't import or open

I have a QM file that was built in an older version of 2013. It opens fine. Now it has been altered and saved. It does not open. I get an error that it was created in an older version of QM and could be corrupted. Other people on our team, however, can open it just fine. We all have the same QM version. I have uninstalled and reinstalled QM - to no avail.

So then I thought, I'll try to import the file into a blank QM file. Now I am getting this message.

The project '<C:\Users\xxx\Documents\My Templates\AssessmentTemplate_MSLMS_newdraft2013.quiz>' cannot be opened. Please be sure it is not open in another instance of Quizmaker."

Any ideas? Suggestions? I am not running this off a server or USB - just my regular Windows 8.1 PC.