[ODE] Step fast issue?

[DjArcas]

I've been using with normal Step for a while now, and I've just gone across
to stepfast. Generally speaking, it's briliant, fantastically fast.

However, I seem to have run into a situation where the physics simulation
just breaks when using step fast.

I have a box, with another box attached to it, and a sphere attached to that
box, like this:

||||||
  |
  |
 O

They are attached using ball joints, in a Thrust sort of a style. I am then
using the Plane2d joint on these.

If the sphere collides with another object, I create a ball joint between
the sphere and the collided object - allowing the 'ship' to carry objects
around.

This works perfectly with dWorldStep, but if I use dWorldStepFast1, what
happens is that the sphere detaches, and sits half way between the cable and
the attached object. The attached object doesn't move. I've tried iterations
all the way up to 360 with no success.

If I comment out dWorldStepFast1 and uncomment dWorldStep, it works
perfectly.

Ideas? (I'm totally stumped! :)

Thanks in advance,

Adam