When specifying a valid FTP proxy, clicking on my FTP:// links does not work at all. When the proxy is not used, all FTP:// links work fine. The proxy I am using sits on port 8080. The HTTP proxy on the same port at the same address works fine. (The proxy does support both FTP and HTTP)
*** This bug has been marked as a duplicate of 33122 ***
Verified dupe of bug 33122: "Can't download FTP file through proxy"