Take a look here and see if any of these can help you:Linksys FAQ
I see you have WRT54G V5, I have the same router, but I have v8.0. You need to update your firmware. In the FAQ from Linksys, it will tell you how. Hope this helps you.
Just an added note, type in your browser 192.168.1.1 click go, it should bring up info on your router. After you get done changing or whatever, I would print out a copy of your settings in case you forget them.