I had this exact problem the first time I installed RunUO. You have to open ServerList.cs and enter the IP address of your server in this section:
Code:
using System;
using System.Net;
using System.Net.Sockets;
using Server;
using Server.Network;
namespace Server.Misc
{
public class ServerList
{
/* Address:
*
* The default setting, a value of 'null', will attempt to detect your IP address automatically:
* private const string Address = null;
*
* This detection, however, does not work for servers behind routers. If you're running behind a router, put in your IP:
* private const string Address = "12.34.56.78";
*
* If you need to resolve a DNS host name, you can do that too:
* private const string Address = "shard.host.com";
*/
public const string Address = null;
The last IP address that RunUO will list in the server window should be the IP address you want to put in place of "null" in the bold line. Also, if you are behind a router you will need to setup port forwarding to allow the incoming connection request to reach the correct computer. Depending on the router you are using, here is a helpful thread:
http://www.runuo.com/forum/showthread.php?t=2068
Hope that helps. By the way, there is a lot of similar questions answered in the Server Support forums. Browse through there or search through there and it will probably answer a lot of your future questions regarding server side problems.
-Kriggle-