Word 2002 changes characters to symbols

Workstation running winxp sp1 (fully updated) and Office XP (fully updated) in a win2k domain. While the user types in a document, Word spontaneously starts changing text to symbols, basically making it gibberish. Tried doing a repair, didn’t help. Tried uninstalling/reinstalling, no help. Word also sometimes changes layout (paragraphs, bullets)for no apparent reason. Has anyone else run across this?