I'm working with Smileys with an expanded select box and a disabled dialog window.
Because of the latter, there is no "more" link, and so everything inside the field set is set to floating: left. This causes the field set to display incorrectly, showing the bottom border halfway through the smileys.
I've tracked the issue down to theme_smileys_select_table, where perhaps it should check if $more returned a value, and if not, compensate accordingly. Sticking a "clear:both" something right after the .smileys div seems to solve the problem.