For a specific static IP on Ubuntu, configure it in /etc/network/interfaces. Show us your work.

If your client's wireless interface has a different IP address, the server may refuse to connect. Check the DNS and Strict setting in /etc/ssh/ssh_config. I've had an issue where "host.domain" vs just "host" being listed first in /etc/hosts caused enough of a mismatch.

Also check the known_hosts and authorized_hosts files. They contain user or user@host or user@IP entries which may not match. Also check AllowUsers in sshd_config. Is it username or username@hostname.c

When you try to login, use the -vv or -vvv option for debugging at the client's side.

-snip, I'll edit this in the morning-