fopen will, apparently, always open a pasv mode data connection (to a ftp type url). Most ftp servers return a code of:
150 "File status okay; about to open data connection",
but in some cases they return a
125 "125 Data connection already open; transfer starting."

(It really depends on the server. WarFTP will return a 125);

fopen works fine when a 150 is returned. It breaks when a 125 is returned instead.

I *think* the only change needed is in line 418 of
ext\standard\ftp_fopen_wrapper.c (based on 4.3.1 source), but I can't compile it to check. :(

Currently it reads:
	if (result != 150) {
and I think it should be:
	if (result != 150 && result != 125) {

References:
RFC 959
also see ext\ftp\ftp.c
     lines: 683, 765, 1473, 1581, and 1694
(the ftp functions all work fine in both passive and active modes).