I know this thread is very old, but i just noticed that i have more or less the same problem. When connecting to glFTPd site with SSL i get:
AUTH SSL
234 AUTH SSL successful
Negotiating SSL/TLS session...
USER kungfuzius
421 Failed TLS negotiation on control channel, disconnected
Connection failed
Delaying for 120 seconds before reconnect attempt #1
Very strange, because i'm really sure that SSL is turned on on the server, because with IglooFTP for example, i can connect with SSL but the client suxx

Would be very nice if anyone will find or has already found a solution for this problem.
I'm using FlashFXP in WineX 3.
Thanks in advance
kungfuzius