All of a sudden my ssh connection to server has been damaged. Here is what's happened:

$ ssh -vvv -p <PORT> -l <USER> <HOST>
OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /home/khosrow/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to <HOST> [<IP>] port <PORT>.
debug1: Connection established.
debug1: identity file /home/khosrow/.ssh/identity type -1
debug1: identity file /home/khosrow/.ssh/id_rsa type -1
debug1: identity file /home/khosrow/.ssh/id_dsa type -1
ssh_exchange_identification: Connection closed by remote host

I've recently updated the box with yum update and sshd got updated as well. I honestly don't know if this caused any damages or not. But it's prompted that /etc/ssh/sshd_config was stored as /etc/ssh/sshd_config.rpmnew which was quite normal.

I've seen similar posts while googling, but almost all of them suggests that I should check /etc/hosts.allow and /etc/hosts.deny, which in my case, I can't. I can not connect to the box to see what's going on there.

I rebooted the box, through web interface of server provider, and it even got worse. I'm now getting this:

$ ssh -vvv -p <PORT> -l <USER> <HOST>
OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /home/khosrow/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to <HOST> [<IP>] <PORT>.
debug1: connect to address <IP> port <PORT>: Connection refused
ssh: connect to host <HOST> port <PORT>: Connection refused

with both <CUSTOM_PORT> and default 22 ports.

I would really appreciate if anyone could help me on this.