Have observed problems with spellcheck in Mail.app, it will lose focus and cease to work correctly after correcting about 3-4 words. Also new issue after webkit 522.11 upgrade. It appears as if the spellcheck dialog can no longer locate the email box so it gets stuck and is unable to find anything else in test document. Closing and redoing works again for a few more words before behavior happens again.
I've now noticed spellcheck behavior problems in Safari and textedit too. In safari it sometimes loses the focus and can't find spelling errors in text field being checked. Heh, I even reproduced the bug spellchecking this comments field. In Textedit spellcheck can only be run on a document once, if you run it again it will not check for the same errors twice. it automatically ignores everything that was checked first time even if you ignored them the first time.
Adam, does this still occur with the latest versions of Safari and WebKit?