Go to system-->administration-->network, and make sure your hostname is set in the 'general' tab.
If that looks ok but isn't working for some reason, you can add your hostname manually. Just add this line:
Underneath the '127.0.0.1 localhost' line of your hosts file with a text editor.
You may need to restart networking after doing this:
Added: Just saw the '192.168.1.80 geko80' line. I'd take this out. It's better to use the 127.0.1.1 form above for what you're doing because it will never need to change and will work even if the network is down.
sudo /etc/init.d/networking restart
Still, I think what you had should have resolved, so you may have a different problem. If the above changes don't work, check your /etc/nsswitch.conf file, and make sure that 'files' is first on the list after 'hosts:' on the 'hosts:' line.