Word error message when saving

[francesemba]

I'm 4 weeks from finishing a dissertation and for the last 2 days after working for 2-3 hours pressing save all the time when I tried to save it again (a word document) I get the following error message "a file error has occurred check your network connections or make sure the disc is properly inserted and not defective" and I have to then not save amendments to be able to close the document.

please help