Word bugs - document map

For a doctoral thesis you have to write a l-o-n-g document with several chapters, contents, appendices, so you need to use styles, but Word 2007 sometimes changes styles such as captions to a high level, which messes up the document map. I think I've found the trick solve this problem.

Go to Word options, then proofing, and choose the auto correct tab. Then AutoFormat As You Type. Untick 'Define styles based on your formatting'.

I've shown the relevant window in the picture.

However, you still have to unmess the captions. The quickest way to do this seems to be to select a piece of normal text, right click its style box, and choose update style to match selection.
Then watch your document map refresh itself back to what it should look like.