CFM, ERP, stepsize, bNormalizationResult failed

Hi,
I'm simulating a 6-wheeled mobile robot with a rather complex suspension
mechanism (parallel and closed kinematic loops). I get it to work but only with
a "spongy" behavior. I've been experimenting with the CFM, ERP and simulation
step parameters. The "hardest" constraints I can impose are: ERP=0.9 and
CFM=0.001 at a step size of 0.005.
Even if I set ERP to the default 0.2, I can't get any closer to the default
value for CFM (9.9*10^-6). This means that the rover cannot be simulated with
default ERP and CFM because l get an error that "bNormalizationResult" failed.
Any ideas?
With the current settings the rover is not stable in its initial state, i.e. the
suspension is bending under the load of the body even though everything is made
of rigid bodies. This indicates to me that ERP and CFM are too "soft". How can
I fix this problem?
Thanks for any help.

Thomas