problem with ftpd (wu-ftpd and proftpd). Network freezes when I download/upload locally

["Jørn André Berntzen [Nick: Nor]" <jabern00@grm.hia.no>]

Hi!

I'm using Debian with kernel 2.2.19 as a router for my home network doing 100Mbit inside and cable outside.

I am using proftpd as a ftp server, but it freezes when I download/upload locally from my Windows XP machine inside in the house.
It all starts ok, giving me 6000kBytes or so in the beginning, but then the transfer-rate diminishes 
to 0.0Kbytes in a few seconds and Debian freezes every network connection inside the house.
But when I log into Debian at the machine itself - connection outside seems ok. 

So I use ifdown -a and ifup -a  to get the network up and going again, but ftpd freezes when I try anew.

Have anyone of you had this problem?
I'd be pleased to hear some suggestions of how to solve this. 

Greetings, 
Jorn Andre.