Unfortunatley your ISP is known for shaping bandwidth when it comes to p2p usage...
Michael Geist - The Unintended Consequences of Rogers' Packet Shaping
Had you been doing alot of downloading before this connection problem started ??
What happens when you go here
http://www3.limewire.com:6346/ ??
The page should say 'Your test worked!'.
Your Firewall could be due to your modem/router having a Nat Firewall within..
Have a look underneath the black box that connects you to the internet and see what the make and model number is and let me know...