Having used Limewire in the past i maybe able to help. You are thinking in the right direction when you checked your firewall, as it is being "blocked" from making it's connection.
What connection are you,,adsl,broadband,cable,satellite, then how are you connected via type of modem or are you using a "router". You have have a NAT problem if it is a router. Check your routers settings and allow Nat settings.