[ODE] friction + collision problem

[Santi Ontañón]

Hi, I've already sent this question in another message, but I resend it 
with a proper subject ;)

My problem is the following one:  If I set friction "mu = dInfinity", 
everything works fine. But if I set friction = 0 or 1 (or any other 
small constant), two of the boxes of my simulation enter one inside of 
the other (while ODE gives messages: "LCP internal error, s <= 0 
(s=0.0000)"), and suddently they collide with such a strength (since 
they are one inside the other), that both boxes run away of my simuation 
field.

more details of my simulation: there are 3 boxes, two of them attached 
with a "ball" joint, and there is a flat ground (I allow a maximum of 4 
collision points among each pair of objects)

Should I always set friction = dInfinity? I'd like to have surfaces with 
lower frictions... do I have to do something special to support them?

I've been searching in the archives of this mailing list, and I've found 
2 other people experiencing the same problem than me. However, they got 
no answer... :(

thanks in advance!