I use curl to release new versions of software to ftp.gnu.org.  I use curl in
this manner:

curl -# -T [filename] ftp://ftp-upload.gnu.org/incoming/ftp/

It's an anonymous login to upload, but files without known GPG signatures are
thrown out.  Verified files are moved to ftp.gnu.org.

I found that the most recent version of curl failed to login to the server.  I
looked at it more closely and found that curl was sending 'USER anonymous' then
'PASS ftp' even after it received code 230 after the USER command. 
230 means you are now logged in.

I dug through the code and found the problem.  Here's the fix:

diff -up curl-7.16.4/lib/ftp.c.230 curl-7.16.4/lib/ftp.c
--- curl-7.16.4/lib/ftp.c.230   2007-07-01 18:01:19.000000000 -0400
+++ curl-7.16.4/lib/ftp.c       2007-08-09 15:41:10.000000000 -0400
@@ -2372,7 +2372,7 @@ static CURLcode ftp_state_user_resp(stru
   (void)instate; /* no use for this yet */
 
   /* some need password anyway, and others just return 2xx ignored */
-  if((ftpcode == 331 || ftpcode/100 == 2) && (ftpc->state == FTP_USER)) {
+  if((ftpcode == 331) && (ftpc->state == FTP_USER)) {
     /* 331 Password required for ...
        (the server requires to send the user's password too) */
     NBFTPSENDF(conn, "PASS %s", ftp->passwd?ftp->passwd:"");

Pretty simple to fix.