[ODE] problems with hinges and cycles

[Graham Fyffe]

Hi, I'm getting a bad problem.  I have a cycle of objects connected like
this:

body1 - hinge on x axis - body2 - ball joint - body3 - hinge on z axis -
body4 - hinge on x axis - body1

Basically, body1 has the other bodies dangling off of it in a cycle. 
The problem is, if I add a force to body1 that should cause it to spin
around the z axis or the y axis, it does not spin.  Body1, seems to be
"globally" constrained to x axis rotations only.  There is nothing else
connected to body1.

To experiment, if I change either hinge on x axis into a ball joint
instead, body1 regains all of its rotation freedom.  Similarly, if I
break the cycle anywhere.  So, there seems to be a bug in ODE with
cycles that contain hinges on the same axis, causing the body connected
to the hinges to be constrained to rotation on that axis :(  In case it
makes a difference, I am using WorldStep.  QuickStep seemed pretty
unstable with this setup.

Can anybody verify this, or better yet, suggest a work-around or a
bug-fix?  I can post code or diagrams or whatever else might help solve
this.  I'd really appreciate help on it, and might even be able to
provide cash, because I am on a tight deadline :O  Thanks everybody!

- Graham Fyffe
president, Happy Digital