1.8rc1 sortable#over method bugged -- called along with #sort instead of on mouseover
jQuery UI 1.8 (all versions, including the new RC1) call #over (seemingly) at the same time as #sort. #sort gets called very often since it's hooked into mousemove, so for #over which supposed to be called only occasionally this is quite a problem.
1.7.2 behaviour calls #over only when the mouse enters the draggable/droppable/sortable area, as expected.