btw, I've managed to build a "ps aux" (cut/paste through X mouse) command and saw that the process "keventd" was dead .. actually, switched to Zombie state ! I've tried to rebuild the kernel with optimization "pentium3>gcc31" instead of "pentium4>gcc31", but it didn't change a thing.
It also seems to happen more frequently when i'm using a ppp-over-ssh vpn on a cisco 350 wireless pcmcia card.
I'm really lost and have no idea of where might be the problem.