All I know about is the Access Key which is a 6 character alpha string found at Tools > Options > Media Network and under the top string "Use Media Network to share the library and enable DLNA".
That is correct. But to connect to the server you must use the server's Access Key on the laptop. The error message means that you are trying to use the laptop's own key to connect - in effect, you're trying to have it connect to itself.
So you need to get it from your server (Workstation) and enter it on your client (laptop).
The other possibility is that you copied/restored your database and now you have the same Access Key on both machines. If that's the case, then you need to change the Laptop's Access key by clicking it in Options and selecting 'reset'.
Anyway, if you don't plan to use MediaCenter while outside your house (via internet while on the beach), then using the IP address is fine (though it's recommended that you setup your Workstation with a fixed IP so it doesn't change). Using the access key gives you remote access (and takes care of changing LAN IPs, I think), but remote access may not work anyway until you also configure your router and/or firewall.