Word 2007 changes Outline Level automatically

What's happening:
When I save my document with the Document Map open, close it, and then
re-open it, it automatically randomly assigns Level 1 to my paragraphs.

Workaround: If I fix the outline level, close the document map, and then
save the document, it doesn't reassign the outline level when I re-open the
document.

I write manuals for a living, and this is a major annoyance. I'm working
with 200-300 page documents, and the Document Map is essential to navigating
through the document as I'm writing. Having to fix this each time I forget
and close the document with the document map open has gotten very
aggravating. Is there something I can do to permanently fix this?

I've tried reformatting paragraphs, recreating the TOC, clearing direct
formatting(everything is style-based), and there is something about certain
paragraphs that just won't be cleared so that the Document Map doesnt' pick
it up.