.Net Library Can't get connection to server

 SessionOptions sessionOptions = new SessionOptions
                    {
                        Protocol = Protocol.Sftp,
                        HostName = "ftp.de",
                        UserName = "user",
                        Password = "pwd",
                        SshHostKeyFingerprint = "ssh-rsa 1023 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx",
                                            };

                    using (Session session = new Session())
                    {
                        // Connect
                        session.Open(sessionOptions);
                    }

SshPrivateKeyPath = "C:\\temp\\",

. 2013-04-10 09:32:54.330 Looking up host "ftp"
. 2013-04-10 09:32:54.330 Connecting to xxx.xxx.xxx.xxx port 22
. 2013-04-10 09:32:54.408 Server version: SSH-2.0-OpenSSH_4.3
. 2013-04-10 09:32:54.408 Using SSH protocol version 2
. 2013-04-10 09:32:54.408 We claim version: SSH-2.0-WinSCP_release_5.1.4
. 2013-04-10 09:32:54.455 Doing Diffie-Hellman group exchange
. 2013-04-10 09:32:54.549 Doing Diffie-Hellman key exchange with hash SHA-1
. 2013-04-10 09:32:54.720 Verifying host key rsa2 0x23,0xd with fingerprint ssh-rsa xxxx xx:xx:xx:xx:xx:xx:xx:xx:x:xx:xx:xx:xx:xx:xx:xx
. 2013-04-10 09:32:54.720 Host key matches configured key
. 2013-04-10 09:32:54.720 Host key fingerprint is:
. 2013-04-10 09:32:54.720 ssh-rsa xxxx xx:xx:xx:xx:xx:xx:xx:xx:x:xx:xx:xx:xx:xx:xx:xx
. 2013-04-10 09:32:54.720 Initialised AES-256 SDCTR client->server encryption
. 2013-04-10 09:32:54.720 Initialised HMAC-SHA1 client->server MAC algorithm
. 2013-04-10 09:32:54.720 Initialised AES-256 SDCTR server->client encryption
. 2013-04-10 09:32:54.720 Initialised HMAC-SHA1 server->client MAC algorithm
. 2013-04-10 09:32:54.829 Reading private key file "c:/temp/key.ppk"
! 2013-04-10 09:32:54.829 Using username "username".
. 2013-04-10 09:32:54.861 Offered public key
. 2013-04-10 09:32:55.235 Offer of public key accepted
! 2013-04-10 09:32:55.235 Authenticating with public key "public key"
. 2013-04-10 09:32:55.235 Prompt (3, SSH key passphrase, , Passphrase for key "public key": )
. 2013-04-10 09:32:55.235 Disconnected: Unable to authenticate

SessionOptions sessionOptions = new SessionOptions
                {
                    Protocol = Protocol.Sftp,
                    HostName = "host.com",
                    UserName = "username",
                    //Password = "xxx...xxx",
                    //SshPrivateKeyPath = @"xxx.ppk",
                    SshHostKeyFingerprint = "ssh-rsa 2048 ..."
                };