hm ... gnotella was actually the slowest servent i tried out so far. but even gnotella just lagged itself - it didn't lag the system though. currently i get high cpu usage only when all host connections are established from scratch. because there is so much traffic then i guess. however, what os are you running? on my 500 athlon everything is fine and i watch movies in the background and burn cd's simultanously, so something seems misconfigured.

btw, i had a broken network card once, that worked but made the whole system stand still whenever it was sending tcp/ip packets. maybe its a hardware problem?!?