Problem about ssh client connection

[roberto giovoni]

I have an ssh process running on unix_bsd based server.
Normally to connect remotly to this server I use a putty
terminal (running on windows XP client).

Now I have the following problem:

when I open a client terminal connection (with a putty terminal)
the message "login as: " is normally displaied.

After I insert my login usermane followed from return key press.
I wait for "password:" message request but it isn't displayed.
Moreover after about 1 minute the putty terminal session is
automatically closed.

On server site the following message is displaied:

"fatal: Timeout before authentication for xxx.xxx.xxx.xxx"
where xxx.xxx.xxx.xxx is client IP address.

Can someone help me to understand what' s happen?

Thanks for your help in advance and excuse me for my 
bad english.

			Giovoni Roberto