MS Word Formatting GoneHaywire

I'm using Microsoft Word 2002. If I select a complete paragraph (including the paragraph symbol that is displayed when the Tools -> Options -> View tab, "All" box is checked) and then apply bold (using either Ctrl+B or the Bold toolbar icon), my entire text becomes bold. If I click the Undo toolbar icon or use Ctrl+Z, the paragraph I selected remains bold and the rest of the document is restored to the way it was before I applied Bold. The same thing occurs when I use Italics and Underlining. Any ideas? Thanks!

P.S. This also occurred on occasion when I used Word 97.";