I only gave you info about Pro updates because you asked about downloading a fresh copy of Pro. LW don't keep old installers for download (apart from the last LW 4.18.8) & so if you wanted a Pro installer, you'd need to have current benefits to download.

AFAIK Comcast aren't blocking p2p any more - use Google to search for Comcast blocking p2p & you'll find info about the lawsuit etc. And if your test worked then it indicates that LW's default port isn't being blocked.

But regardless of that - did you try any different listening ports in the recommended range? Does every computer on your LAN use a different listening port for LW? If each computer is using LW then they'll need to have different listening ports. And if port forwarding's in place then they'll each need their own static IP address & port forwarding rules within the router setup.

After you deleted LW's preferences folder, did you have to go through the setup wizard again? Did you have any problems with replacing the gnutella.net file?

Before you set up port forwarding, did you set up a static IP address? PortForward.com - Free Help Setting up Your Router or Firewall

And did you use these instructions for port forwarding?: Port Forwarding for the Belkin F5D9230-4