Thank you for the help, Lord of the Rings. Yes, I am using XP, but my XP firewall was disabled. Also, my UPnP is enabled. But after asking around here, I believe my problem lies in my school's firewall, which I don't have access to. In fact, I've opted to uninstall LimeWire because my college will revoke my rights to use their network if such a program exists on my computer.

Thanks again for your time and advice, and I apologize for any inconvenience.