Rubber band limbs revisited

I keep running into this same problem with the animation between two keyframes giving some really unexpected results, and I'm not sure what's causing it.

Now, this has nothing to do with frame 1 and 2. This happens well along in the animation after everything seems to have started off smoothly.

As an example, I would have one keyframe and 90 with the model standing up straight. The next keyframe would be at 120 with the right knee bent and slightly crossing over in front of the left, really only a few inches of movement. The problem is instead of the knee going from point "A" to point "B" smoothly, it seems to go from point "A" to "J" to "V" to "N" to "X" to "pi * 1.02645478 / the inverse ratio of every needle in every haystack" and then finally to "B" thirty frames later.

I'm using Poser 5 btw, and would really like to know how to correct this. I just can't see what would be generating this bizarre movement. Even on frame 91... instead of starting to move towards where the end position would be on 120... the limb starts moving in the opposite direction instead and contorting in inhuman ways.

Any help would be well appreciated. Thanks.

your problem is the spline.

Go into your keyframe editor thing. highlight all of frame two and hit the button called 'break spline' (you have to hover over it to get the words)

If this doesn't work, try it at the keyframe right before the goofy movement.

Like:
Frame 30 is keyframed. Frame 40 is keyframed. But inbetween 30 and 40 say the arm moves back before it moves forward. So break the spline on keyframe 30.