problem with ftp browsing

I have a php script that is like and ftp client, only is just browsers the server and displays file names and folders. If you click on the name of a folder that it displays, it will then display the files and folders inside that directory, and so on for all directories. It works perfectly when I connect to my internet hosting company through ftp to browse, but it doesn't work right when I connect to my personal ftp server. I have tried using both Serv-U and Bulletproof ftp servers to host my ftp site. The script won't display my server correctly with either of these. Can anyone give me some advice? I would really appreciate it. Thanks. Matt