NAT router/Firewall
 

My LimeWire does not download anymore. I keep getting Need More Sources. I recently downloaded another shareware software, and it told me right off that I am behind a firewall and/or have a NAT router that keeps me from downloading files. Could this problem be the source of my downloading troubles? And if so, is it safe to disengage the firewall - would I be opening myself to a slew of viruses?

Thank you in advance.