Because I know Word has a history of not liking very large documents (my supervisor specifically told me not to use LaTeX... grr), I decided to learn the Master document / subdocument feature of Word when writing my PhD thesis. I have the title page / table of contents etc in the master document, and each chapter as a separate document. However, when I save the master document, it appears to save all the chapter documents apart from one (Chapter 4), for which it brings up the Save Document dialog box, helpfully with "Chapter4.docx" in the "Save as" box (n.b. Chpater4.dox is not open). Clicking save does nothing, and doesn't make the dialog box go away. Saving as a different document means that my changes aren't reflected in the same document. There must be some reason Word doesn't like this particular document but I've got no idea why - there's nothing special in it that isn't in any of the other chapters.

I have tried closing all documents, renaming Chapter4.docx, opening the master document, expanding all documents, OKing the warning that Chapter4.dox does not exist, and inserting the 'new' document, but even when I save the master document it still won't save the new Chapter4 document.

If anyone knows any reason why Word is acting like this (or if I'm doing anything stupid), I'll be eternally grateful

(p.s. sorry for the long rambling message. It's late; I've been working on my PhD 4.5 years, I really really want to throw this computer out the window, and I hope people are kind enough not to downvote this question because of it's rambling nature!)

Update

With Word closed, I've tried to delete Chapter4.docx (having made a backup!) - but I get a warning that it can't be deleted because it's open in Microsoft Word... these files are on a network drive and the same problems are happening on 2 different computers. I could login to the filestore through ssh and force the file to be deleted, but I'm curious to know why this is happening!