I have the built-in firewall disabled and my router has the 6112 ports correctly forwarded so it's not my router's problem, proof of that is that when I reboot on the same computer using Windows XP I can host games without any problem.
Any mac players out here that know how to fix this?
edit: I've also tried doing some stuff over the terminal without success such as:
+ Show Spoiler +
ipfw add allow tcp from any to any 6112
ipfw add allow udp from any to any 6112
ipfw add allow udp from any to any 6112
Any ideas?