Hmm, that's a very interesting quirk. I wonder why it's not firing the detach event in that case. Unfortunately behavior attachment/detachment is purely an IE thing so I'm doubtful there's anything that can be done about it programatically, but I'll keep the testcase and look into it at some point.

I'd like to get back to the main issue, though, which is the slow dragging performance. Do you perhaps have a testcase which demonstrates that?