You will both need to get rid of that firewall to be able to direct connect to each other...I know that you have allowed limewire as an exeption, but the firewall that is blocking you would be a NAT Firewall which is built into your Modem/Router...
Any way just to be sure this is the problem could you post these details please...You may also want to get your friend to do the same...
System details - help us to help you