Robot arm zero joint velocity not working

Hi,
I am experimenting some problems trying to get zero velocity on a joint. I have
created a robot arm using ODE hinge joints. 
Each link of the arm is an ODE box body with 1 unit of mass. For the robot arm
motion, I am setting the motor parameters dParamVel and dParamFMax. It seems to
work correctly for non-zero velocity, but if I try to keep a joint with zero
velocity (or small velocity), the joint is still moving, because of the effect
of gravity on the following links. It is still moving even if I set dParamFMax
to a very high value (10000 and more!!).
I have configured the arm links so that they are not affected by gravity. This
solves the problem when the arm is not in contact with the environment. But if
a contact appears, the contact force is transmitted to all joints, and they are
moving even if I indicate I want zero velocity on them with a big FMax. 

Any help would be very appreciated.
Thanks in advance.