I even got the "dislocated IK-parenting joint" bug when I made an AVI movie of my rebreather diver swimming with his breathing bag inflating and deflating. The inflating and deflating happens by changing settings on a morph on the part "rebrbody" of his rebreather set. That part is part of the IK-circle "chest, neck, mask, breathing tube segments, rebrbody, chest", but the inflating and deflating does not move any joint angles; merely touching an IK-circle during a movie was enough to make my Poser 4.0.2 switch that IK-chain off and on again and thus activate this bug. (It also happens when I move his head as he swims, and that does change joint angles in that IK-circle.)