This looks like a corrupted font. It's unusual and might be difficult to find.
You can try (1) to repair or (2) uninstall/install Word, or (3) use the Office 2003 Removal Wizard (can be downloaded from microsoft) to erase Office completely, then reinstall. It won't hurt, as long you have the Office XP CD at hand.
Can you do a system restore to a previous state when things still worked correctly?
Or consider contacting Microsoft. They might tell you what fonts to uninstall/reinstall in Config Panel>Fonts.
Kees
Whenever i open a word document with an equation in it all the mathematical symbols are wrong. They look like they have been substituted with wingdings characters! When i click on the equation as if to edit it, it sorts itself out but the equals, addition, subtraction signs etc are missing. Any ideas on how i can fix this?
I'm using MS Office XP Professional. Cheers

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic