That's what I don't understand, though. I don't have problems with my internet. Could it be because I'm behind a router? I thought I opened the correct ports, but maybe I'm wrong

Opening ports and enabling DMZ host did nothing to solve the problem.

I didn't have to open any ports on my router, and I'm also running Vista.

Perhaps the Windows Firewall software is blocking UO? (Ya know how the first time you run a program, it says it is being blocked and you have to click the "unblock" button). Any chance that's the problem?

Good point Kit! I had to allow access for UO and every time we get a new patch I need to update Norton Anti Virus! (Create a new rule)

I don't know, then. I don't have AV software installed right now. Windows Firewall is set to allow UO to access the internet. When I load up the client, the main page isn't displayed and says I don't have an active internet connection, which I obviously do. The more I keep trying to get this to work, the more disappointed I become

Edited to add: I was reading on the main page of UO, and I wonder if the reason I can't connect to the server is because they're going offline tomorrow?

The servers have been down but they are up now. If you are still having trouble have you tried, disabling all firewalls and anti virus etc, If it works you have limited it down to those programs.