This error is caused by problems in your hosts.deny. If you installed all the recommended packages in Ubuntu, you’ll most likely have Denyhosts. If not, /etc/hosts.deny won’t exist, thus this tutorial will not apply to you.
First, ssh to your server via another IP
Open this file:
nano /etc/hosts.deny
Find your IP, and clear the line. It’ll look like:
sshd: [your ip]
You can put # symbol to comment it if you want.
Now lets save and exit out of nano, and restart SSH.
/etc/init.d/ssh restart
Done. Log out, and log back to verify.
If this problem will often repeat itself, so lets fix it so it won’t happen again.
Open this file:
nano /etc/hosts.allow
Scroll to the very bottom, and type this on a new line:
sshd: [your ip]
Save nano, and exit out. Then, restart SSH.
/etc/init.d/ssh restart
Voila, problem solved!