[ODE] problem with 3 contact joints

[Jacob Van Wingen]

I'm new to ODE - attracted by the Freefall buggy demo.

I've run into a problem while setting up a simple test program.

In the test there is a bounding box defined using 6 planes, with no body attached and 2 spheres of equal mass thrown randomly into the box.
The spheres roll and collide with each other nicely in the box, however when a sphere rolls into a corner of the box it begins to sink into the ground plane and then shoots straight up at a very high velocity. This also occurs if a sphere is touching the other sphere and two walls. It always appears to sink into the ground plane.

my dSpaceCollide callback seems to allow for more enough collision points.
the world ERP is set at 1.0 and the problem occurs even with very small time-steps.

has anyone else encountered this problem, or know what's going on?
thanks,
Jacob