I want to document my experience with with proftpd in the hope that it will help someone that has not been through it before. I am working on debian 5.05 with a desktop install. When you install proftpd and can not connect or can connect only through active ftp. Here is the steps I think you should go through before you pull out your hair or post. First go to your router and check that. You need at least port 21 open and I needed port 20 open also. Then make sure your passive ports above 1024 are set up.
Next make sure linux is set up to except connections on 21,20 and your passive ports. All this you will find on almost any site about proftpd but with about 30 sites bookmarked only one place I found has this info marked. You must load ip_conntrack_ftp for passive mode to work. My debian install did not do that and the people helping you assume it is loaded I guess because no one told me I needed it. There is a webpage out there with a list of conntrack modules but I lost it so maybe some one will add the link. Also and I only noticed this because debian is the flavor I like, all the best sites for a newbie on iptables seem to be redhat? Maybe someone with more knowledge on the subject will fill in the holes and add explanations. I do not know and have not researched the why but If you can not connect to a new install of proftpd check this stuff first. your experience with proftpd can be a success and for the most part painless.