File name changes to Word Work File D_ and Deletes itself.

Hi There,

Hope someone can help - I have a problem that I don't know if someone else may be experiencing as well.

Essentially I created a word document and given it a filename. As I keep on writing I regularly save the document, but at some point I can see that on the top blu banner (where the file name is written) the name of the file changes to Word Work File D_# (where # is a number).

If I close the file, the document deletes itself.

If I keep on writing after a while the word closes and the document deletes itself.

If I try to open it again in the list of recent files, the a message appears saying the document cannot be opened, because the file has been deleted.

Can anyone help please?

Thank you so much.

(Office 2011 for Mac)