That problem is easy to resolve: Use the hosts file, Luke. ;-)
Ok, I'll get into more detail:
The cause of your problem is this:
a) Your router most likely doesn't support the local loopback feature (most routers don't).
b) Geeklog uses absolute URLs for its resources (graphics, pages, whatever). For example, http://your.url.here/layout/Gameserver/theme-images/gameserver_logo2.gif is the URL to the Logo of the gameserver theme.
What happens is this: Your browser is asked to get several files from a specific URL (see b)), looks up the domain via DNS, gets the IP it has to ask, sends a request for the pages to the specific IP and times out because the router can't send the request back to your computer because of a).
If your router doesn't have loopback you have to access the computers in your local net with their internal IPs, not the global IP.
To make your domain resolve to 127.0.0.1 use the hosts file. I don't know if Macs support a hosts file, but Unix/Linux and Windows does, so I would be surprised if Macs don't use it.
The hosts file is a simple text file with several lines in the format
which has to be in a specific directory and have the name 'hosts' which tells the OS not to resolve specific domains via DNS but to use the given IP.
So simply put the line
into it and you are set. If the server is on a different machine within your local net put its (internal!) IP there of course (which will probably be in the 192.168.*.* range).
If Macs don't support a host file check the web how to manually resolve specific domains to an IP without a DNS lookup. There must be some way.