Can't connect to SSL server

I am running proftpd 1.2.8 with mod_tls.

I cannot connect to the server, I receive the following error:

Socket connected waiting for login sequence.
220-

******************************************
* PRIVATE SYSTEM *
* *
* If you are not authorized to be here *
* leave now. *
* *
* Use of this system is MONITORED *
* *
******************************************


220 ProFTPD 1.2.8 Server (TARDIS FTP Server) [tardis.localdomain]
AUTH SSL
234 AUTH SSL successful
Connected. Exchanging encryption keys...
SSL Error
An established connection was aborted by the software in your host machine.



what is wrong?

thanks in advance.