UI 1.6 rc6 possible bug

Hi,
I tried to upgrade to ui 1.6 rc 6 today on my site and I've noticed
that when using sortables, after drag-n-drop the opacity remains the
same(like when dragging, i.e. was set to 0.5), but this only affects
Firefox 3 (ie6 and chrome seem to work ok).
Regards & keep up the good work! ;)