Problems with speed and local ftp on D-LINK DI-524

Hi,

I have DI-524 installed to share my cable modem connection to internet.
In my local networks there are 2 PC's and one laptop.
Laptop and one PC works well, connection speed is as good as without the router but the second PC has terryfing slowed down.
But the bigger problem is that it was my local ftp server (OpenSuSE 10.2 with latest patches) - now with router I can't download anything from it. I get "stalled" status even trying only to list the remote directory. When I connect the ftp to any other computer directly, everything works fine.
This PC has 3 network cards (it used to work as a gateway) and on the DI-524's DHCP LEASE LIST I've it 3 times with different IP's and MAC's (beacuse I've tried all of them, thinking something's wrong with network cards) but with the same network name.
I've also noticed that when I try to download ftp via router both computers (downloader and ftp), on the 'Active Sessions' in router management site, are listed only on the UDP to the DNS from my ISP.