DTD error

I'm using RH 11 and Word 2013.

When I want to use Word as my editor I go to my topic list pane, right-click on the topic and choose "Edit with | Microsoft Word" from the appearing context menu.

Word then opens up and displays the message

"Sorry can't open the file ... bla... bla...bla...

Details: DTD is prohibited, Location Line 2. Column 9

This makes absolutely no sense to me.

Any help would be very much appreciated

Am I doing somthing wrong?

Can I fix this and how?

Thanking you

Duran