The bug sounds like something Elina found and patched after the 1.0 release. I'll test your script with the current SVN. 

As general comments:

- with monte-carlo, you have to provide the move set. We really should put up an error if there is no move set :-) I'll fix that.

- Conjugate gradients can get stuck very easily (which is why we are working on a better optimizer). This is especially true with rigid bodies composed of my particles as the atom balls can get mixed in together and CG can never separate them.