Yeah, basically there's a bug in the specific case where you press Move Up/Down, and it tries to move it past the first/last item in the list, because that item happens to be hidden.
The button code says "there's one more, no problem". The view code says "er, not quite" and falls over. I imagine, also, that you might need to press the button twice to push it past the hidden item, if that item is in the middle of the list.
I don't anticipate the fix being too tricky, but this problem surfaced on the Rio Central build of emplode, and got fixed with a quick hack there (since it doesn't matter particularly). The quick hack got propogated to the Rio Car build of emplode. I just haven't had time to fix it yet.
None of this code has anything to do with Alt+drag, so I saw no reason why it should stop working, except if I was overzealous.
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roger