So I've just had some more time to play with this, and it appears that no one can connect to me on RTR either. Well, I've only tested it with one person, but it definitely is not working.
My RTR server is running fine. I can connect to the specified IP address with no problem. When my friend tries to connect, the connection times out, which was basically the same thing that happened with Acefire.
This time, I didn't see any Windows Firewall prompts, although I did allow the executable files for both RTR and the server application through manually.
I then allowed port 655 through Windows Firewall, creating two separate rules for TCP and UDP. They were both inbound rules. if this wasn't the correct procedure, let me know what I need to do to make this work. It was a bit unclear from the instructions whether these ports needed to be forwarded from within my router, or from Windows Firewall.
As a last ditch effort, I disabled the firewall entirely. Still no go. I'm wondering if having VM Ware player installed is creating some sort of conflict, since it creates its own network adapters, but I can't see how that would be the case. Any ideas?