[ODE] head (only head) sinks into the ground

[Verena Hamburger]

Hi everyone

I have a big problem with my dog simulation. Everything works perfect but as 
soon as the lies on the back (or rols over to the back) the head sinks into the 
ground and won't come out because of lack of resistance when he pushes against 
the ground.

I really have to solve this because with this problem may fail my whole diploma 
thesis...  :-(
So please please help me!!! I don't know what else to try.

contact[i].surface.mode = dContactSlip1 | dContactSlip2| dContactApprox1 | 
dContactBounce | dContactSoftERP | dContactSoftCFM ;
contact[i].surface.mu = dInfinity;
contact[i].surface.mu2 = dInfinity;
contact[i].surface.slip1 = .09;
contact[i].surface.slip2 = .09;
contact[i].surface.soft_erp = 1.0; // same effect if it is reduced
contact[i].surface.soft_cfm = 1e-2; // less is impossible because the programm
                                    // will not start anymore
contact[i].surface.bounce = .001;

worldstep: 0.05 or 0.01 same effect

Thanks for your help
Verena