Firefox remembers the state of checkboxes across refreshes. If you test if a checkbox is checked via jQuery, you might not get the actual values out of the DOM, but the cached state from before the refresh. Keep that in mind when testing.
Rails 2.3.5’s has_one: if you build a form for a has_one association, it’ll overwrite the old value, even if you do not save. This is intended, but not intuitive. The old record will be orphaned.