I hope don't saying a very stupid thing, but maybe this doesn't concern netcards or network but with cpu power.
I've experienced freeziong problems in my celerons 1 GHZ with 3.8, but don't with 3.4. I've tryed as test just load both knoppix 3.4 and 3.8 and just run galaga (yes, the game), after few minutes 3.8 freeze it. Not any kinds of problems with high powered processors. Maybe is the 2.6 vs. 2.4 kernel the issue?

bye, max