I do not have an external modem.

I tried changing LW listening port to 64049 with no luck.

This is straight from Sit-co's website but I'm not sure their firewall is part of our internet package though. My friend also has Sit-co, the same version of LW, and the same windows and LW has always worked just fine for him.

6. What's the security level of the connection?
With SITCO, you get the most secure connection to the Internet available today. Our Secure Wireless Internet Access incorporates a robust and redundant security system of firewalls and intrusion detection systems. Your link to us is a one-to-one or point-to point connection. Using a firewall system from SITCO virtually hides you from the Internet while allowing you to have access to everything you need on the Internet. Access the Internet safely knowing you are protected and invisible from hackers and other Internet related insecurities.