I use SecureFileTransferClient an I have the same problem (it worked with Vs 5.2.6)
Log-Snippet:
[10.10.18 11:40:15:712 CEST] 0000003a SystemOut     O DEBUG - Setting custom validator to com.enterprisedt.net.ftp.ssl.SSLFTPStandardValidator 
[10.10.18 11:40:15:712 CEST] 0000003a SystemOut     O DEBUG - Turned server validation off 
[10.10.18 11:40:15:713 CEST] 0000003a SystemOut     O DEBUG - Created connection #5 [free=0,busy=0,max=3,created=1,cleared=0] 
[10.10.18 11:40:15:713 CEST] 0000003a SystemOut     O DEBUG - No limit now set on transfers 
[10.10.18 11:40:15:713 CEST] 0000003a SystemOut     O DEBUG - Setting integrity check to false 
[10.10.18 11:40:15:713 CEST] 0000003a SystemOut     O DEBUG - Turned server validation off 
[10.10.18 11:40:15:714 CEST] 0000003a SystemOut     O ERROR - 5:Connect[vftp.vpiroll.local:21] failed 
java.lang.NullPointerException
	at com.enterprisedt.net.ftp.ssl.SSLFTPClient.enableCipherSuites(SSLFTPClient.java:1181)
	at com.enterprisedt.net.ftp.async.internal.ConnectFTPSETask.preConnectConfigure(ConnectFTPSETask.java:229)
	at com.enterprisedt.net.ftp.async.internal.ConnectTask.connect(ConnectTask.java:153)
	at com.enterprisedt.net.ftp.async.internal.ConnectTask.run(ConnectTask.java:216)
	at com.enterprisedt.net.ftp.async.internal.FTPTaskProcessor$b.run(FTPTaskProcessor.java:593)
[10.10.18 11:40:15:714 CEST] 0000003a SystemOut     O DEBUG - notifyComplete() called: com.enterprisedt.net.ftp.async.ConnectResult@d64e223b 
[10.10.18 11:40:15:714 CEST] 0000003a SystemOut     O DEBUG - Connection failed 
[10.10.18 11:40:15:715 CEST] 0000003a SystemOut     O WARN  - One or more connections failed to succeed - disconnecting all 
Klaus