Are you sure the FTP server is running on the target machine and bound to the correct interface? I have a Linux virtual machine running Ubuntu server 7.10 that I use for web site stuff and had similar problems at one point.
I haven't kept up my Linux practical experience though, so it's difficult to give advice. I think I ended up removing all IPTable entries, but that's not a good idea for a public facing server.
I'm sure someone will be able to point you in the right direction, but otherwise it'll probably be a time consuming trawl through Google results :\
https://www.google.com/search?num=10...n+refus ed%22