proftpd - TLS connection hangs authenticating

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http://serverfault.com – I setup a proftpd server that uses TLS/SSL certificate for authentication. Everything works well when I connect through lftp or Filezilla (with explicit connection). But once I attempt connecting with simple ftp connection from Filezilla, the USER command ends with the 550 response (SSL/TLS required). After that any further connection through lftp or Filezilla (with explicit connection) will hang authenticating. Anyone knows how to workaround this issue? Is there a way to ask Filezilla to automatically use TLS/SSL if required? I am using Ubuntu server 10.04 with proftpd 1.3.2c. There is no e (HowTos)