I downloaded kopete 0.74 for Mandrake 9.2 from rpm.pbone.net.
The msn problem is fixed, but now if I add a buddy in my list, next time I will launch Kopete, the buddy will not be in my list. If I try to add him again, Kopete says it is already in.
An other problem is that kopete shows very old pseudonym of offline buddies. When they get online, it shows the good one, but then do the same things when they go offline.
I think I will downgrade to 0.73 and just move a buddy to an other group to connect to msn.