My main problem is that i don't know wat the problem is, i don't know if it's iptables-related, kernel-related or what. I haven't tried other kernels mainly
because it's a lot of trouble to get the driver of my USB ADSL modem to work
between different kernel versions.
I was using debian woody with a 2.4.19 kernel and everything worked fine,
the problem arised when i upgraded to sarge. The main configuration didn't
change during the upgrade.
Any suggestion on what the problem could be or at least how to trace it
would be much appreciated.
Have you checked 'netstat -in' for interface errors on the ethernet connection, I am suspicious that you just have a duplex mismatch between the host and client. Worth a look.