Using Word 2000 - Heading styles are applying to whole document

[Katiegirl1983]

some, hopefully helpful, history:
I'm using Word 2000 and working on an creating an office manual. There is
over 100 pages with manual section breaks (next page) after each page (each
page is a new topic). I applied Heading 1 to all my topic headings and the
rest as body text. The document was great, I saved. Next time it opened, the
styles had all switched to body text only.

Now, on a page, when I try to highlight the heading and reapply the heading
1 style it only takes on the formatting (bold, underlined, etc.) It does not
however actually change to Heading 1 (it still says Body Text in the box) and
it also does not center align (which Heading 1 is set to do) Alternatively,
if I place my cursor in the heading (without highlighting the whole word) and
attempt to reapply the Heading 1 it changes to whole document to heading 1.

None of my styles are set to automatically update and they are all based on
'none'..
Please Help I've looked everywhere online for an answer and nothing is
helping.

 

[Stefan Blom]

If you make sure to select a whole paragraph, or just leave the insertion
point blinking in the paragraph, before applying the style, then can you
successfully apply the heading style?

If the above does not work, you could try treating the document as corrupt.
Copy its contents except for the final paragraph mark (¶) into a new file.
Does that make a difference?

Note that in order to show/hide paragraph marks, you can press Ctrl+Shift+8.