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Killing Imoen during the slayer dream with an high damage enough hit will disintegrate her
Thus stoping the resolve of the scene, leaving you unable to do anything.
(This scene: http://img15.hostingpics.net/pics/240866Imoenbug.png
Happened to me a few times with high-str charname, killing sarevok/bodhi/irenicus, then critical-hitting imoen, destroying her body, preventing her to say "five".