Ftp & problems

Friends: I have activated in the firewall (SuSEfirewall2-2.1) the services for ftp. When a client computer wants to make a passive or active ftp -with Windows Commander, cuteFTPpro, WSFtp, etc- to the server ftp of the company (ftp.myserverftp.com.ar) the computer that has the firewall (192.168.0.1) freezes, completly freezes; but in DOS mode, works well, very well. I have conected in eth0 the internal lan and in eth1 the cisco 777 router with ADSL line (works fine). Any help? Not you for where to attack the problem. Thanks folks