I am using Google Spell Checker with Vista, and if I click on it the text in the Message window disappears. This only happens on sites running vBulletin 4.0 or higher. No text shows up and you can't tell where the spelling errors are. Also, the ispell spell check that comes with vBulletin, does not highlight the misspelled words, which means you can't tell what word is misspelled. And I also have to install it every time I use it.
Strange behavior because it only happens with site that are using vBulletin 4.0.