<A target="_blank" href="http://www.lntoolbox.com/en/categories/notes-domino/258-interim-fix-available-for-lotus-inotes-that-introduces-support-for-firefox-4.html">Bastian Wieczorek has written up an explanation of the problem between iNotes</A> 8.5.2.2 and Firefox 4. He also provides a link to Interim Fix 401.8HF6 and a workaround from Mozilla.