The problem I'm having is that when a circle (mass 1, radius 1, moment of inertia from cpMomentForCircle()) is added to the Space above it, it falls correctly but upon contacting the immovable body, its x and y coords suddenly become 'NaN'. Just before the collision the y-velocity of the circle=-24 and immovablebody=0, but after the collision (at the same time that the circle's position becomes NaN) the y-velocity of the circle=-12 and the immovablebody=-12. After this, the circle continues to accelerate downwards (according to it's velocity value) but the velocity of the immovablebody remains at -12.

Does anyone have any idea why:

- The position of the circle suddenly becomes NaN (when it should probably just bounce)
- The immovable body suddenly acquires a velocity