MSN6.1 cannot receive and send webcam

Hello!

I have a friend which he have windows XP with all patches
and SP, and he cannot receive my invitation to have
webcam (I want to show me to him). The same probleme
apply in the other way.

In other words:

I click on icon "webcam" to my friend, he accept, and
nothing happens during.. ~1 minute, and after, I have
this message:

Vous avez arrêté l'utilisation de la webcam avec
NICKOFMYFRIEND

(for english readers: you have stopped the webcam with
NICKOFMYFRIEND).

But, if I try with others friends, it's work very well.
Also, before, it's worked... not now. He have a webcam,
and he send his request to me, I accept, and I have the
same effect. But, if he go in tuning video/audio, he can
see him, and it's work very well...

What the problem? (He have reinstalled msn6.1 (uninstall,
and after,n installing, and alway have this problem)

THanks,

J.