Hello! I had the same problem with kernel 2.6.22. I have a very recent Asus P5K-VM motherboard, and with the same harddrive and software on an Asus P5B-VM I had no problem. I have no problem with Ktorrent. When I use amule with only the udp mode (Kademlia), my Debian Etch/Lenny works alright for 24 hours straight, with dozens of active downloads. When I use the regular tcp mode (edonkey protocol), after 3 hours my Debian completely freezes (no hardrive activity, no console accessible, impossible to trigger a reboot from the keyboard with the right sequence of keys), and I have to reboot. I reproduced this more than ten times. I use an old D-Link DFE-530TX ethernet card with which I never had any problem over the years. I have a cable internet connection (1 MB/s up/ 30MB/s down) There is nothing in the logs before the freeze.
I tried with several versions of amule which worked perfectly before on my previous motherboard, I did purges + clean installs of three different versions of amule. I contacted the devs of amule, they said the problem does not come from amule and I agree with them.
I finally also had a freeze after 24 hours of using udp in amule. It means that tcp triggers the freeze 8 times faster than udp.
The problem was solved by I do not know which software update with aptitude.