SSH hangs

Run it as

 ssh -vvv ...

and see the reason.If it stops pending on reverese DNS lookup, check twice your DNS zones for duplicate records.Also restart your DNS server and see what it spits in /var/log/messages.
If it pends in the gssapi-with-mic authentication, edit /etc/ssh/ssh(d) and set

 GSSAPIAuthentication no

Another reason for hang could be slow DNS. SSH uses reverse DNS check of incoming IP address.

 UseDNS no