@Kry: It did happen again, but I think now I figured out what the problem is, aMule does really nothing have to do with it (a least not directly).
My computer has got two NICs, eth0 connected to ADSL modem, eth1 connected to my brothers computer, I have IP forwarding (NAT) set up for his access to internet.
Everything runs perfectly for days and days of uptime (of my aMule), but when he starts aMule (for his aMule I configured TCP port 5662 and UDP 5672, so they don't interfere with my standard ports 4664,4672), on my computer a configured port forwarding for his 5665 and 5672 ports. Under this conditions (both computers running aMule) my computer after cca. 5-6 hours becomes a "zombie", eventually after a day or so it crashes.
It is (I think) a kswap-kernel-iptables-IPforwarding combination problem, aMule alone works 100% OK :baby:

Just to let you know.
thanks for your time and great work,
d