|I assume the router is otherwise working, if not, then back up a step and start over.|
I assume that Safari otherwise works.
Try restarting the computer (clear things out and start clean) and try again.
Try Firefox for Mac (Safari can be real picky sometimes).
Are you sure you are typing the "HTTP://" first before the address (no quotes)? This is required but often forgot.
You have to be a little bit crazy to keep you from going insane.