If you are not connecting at all, then something is most likely blocking LW from connecting. Either a firewall, security software, or your router. I do not believe Comcast block p2p. Re-check your firewall and make sure LW is listed as an exception. Check your router to be sure UPnP is enabled. If you have any other security softwares that might prevent something connecting via the internet, make sure LW is on their exception lists.

Some Windows updates can change firewall settings.

Some 3rd party firewalls now work on a different concept of 'trusted' applications. I was so frustrated with one of these I removed it and reverted to Windows firewall because it had full level 3 trusted status but was being firewalled by that firewall (I was using BearShare 5 and the program's console gave the message it had detected Zonealarm and was being partially blocked. That explains why peers kept dropping off.)

Yes you could try FW4 to see if it connects at all also. FW is based off LW4.