Word – Microsoft Word cannot Save

I use Microsoft Word 2010 to write long documents. These typically include a lot of sections, graphics, formulae, footnotes, a TOC, an index, a bibliography, and inline cross-references and source references. Hence, I make full use of the (mostly) excellent functionality offered by the Microsoft Word word processor.

However, far too often (maybe once a day) when I try to save a document (Ctrl+S) after a few minutes of editing, the "Save As" dialog appears (which is unexpected, since the document is already saved as a file). And, then, no matter if I choose to overwrite the existing file, or to save as a new file, which are my only options, it fails with error message "A file error occurred" [translated from Swedish: "Ett filfel uppstod"]. Thus, I cannot save the document anymore!

Is there any known cure? I have experienced this problem since Word 2007. Now I use Word 2010. [This never happened to me when writing equally complex documents in Word 97 and Word 2003, which are stable as rocks.]

The only workaround that I know of is to copy the text to Notepad, create a new Word document, and spend a few hours reformatting it and recreating all formulae, illustrations, etc.

Some clarification

This has happened for a very long time, and with many different documents. And on different computers. My hypothesis is that Word is buggy, and that formulae and Word illustrations sometimes "mess up" the document so that it cannot be saved any more.

I just removed all equations and illustrations from the file, and then it was possible to save it. But when I undo (so that the equations and illustrations come back), I can no longer save. We are talking about many, many hours of work, so I am a bit annoyed…

Problem solved!

The problem was an illustration, the removal (and recreation) of which resolved the issue: