I don't understand why, but this makes my uber-rig cry (I get down to less than 1fps as well)... Something is seriously wrong with this cap, and I can't put my finger on it yet. going to try something now and see how it fares.
*EDIT*
As far as I can tell, there has to be a bug somewhere in this cap. It seems to be realted to your lerp call in the second to last event. I don't know enough about lerp to check your forumla, but the problem seems centred aroung that particular event.
I've had no luck in pin-pointing the exact cause, maybe someone else will have better luck, but I would be prepared to ready this for tracker submission as a bug if nobody else can suggest a solution.
~Sol