Resetting InDesign's “Document modified outside of book” warning

Question

This feels more like a Super User question than Graphic Design, but I figure someone here will be more likely to know the answer.

Using InDesign 5, I have a "book" collection that I use to keep a bunch of files in one place. Apparently at some point I opened up and modified two of the files apart from the book file, yielding this little warning:

My question is, how do I get rid of the warning, short of removing the file from the book and reinserting it? I figured there has to be a better way. I would have assumed that opening the file from the book, editing, and saving would have reset it, but that hasn't been the case.

Answer 1

"Update all cross-references" from the fly-out menu should do the trick. (sorts it out for me in CS6). It's the equivalent of 'Update all links' in the Links window, for placed files within a document.

Or if that's greyed out, "Synchronise book" might help?