Weird formatting error, please help

I've got a weird problem with MS Office 2003.

I've got a document with 2 paragraphs. The second paragraph is perfectly normal, but whatever formatting change you make to the first parpagraph is then applied to the entire document. I've tried recreating the document, restartig word etc but it hasn't done anything. I've checked the paragraph settings etc and everything looks normal.

It's like one of those problems that you sometimes get with online text editors where the entire page is encased in a hidden paragraph tag and is trated as a single entity.

Weird, huh.