On CentOS 5.5 x64

Symptom:
Taking a long time to bring a ssh login: prompt up

Connecting using:
ssh -v -l username 10.22.23.24

Output:
debug1: Authentications that can continue: publickey,gssapi-with-mic,password
debug1: Next authentication method: gssapi-with-mic
debug1: An invalid name was supplied
Cannot determine realm for numeric host address

debug1: An invalid name was supplied
Cannot determine realm for numeric host address

debug1: An invalid name was supplied

The Fix
open /etc/ssh/sshd_config and change the following:
UseDNS no # didn’t help in my case
GSSAPIAuthentication no # this did work