Hosting issue

[GaryGRK]

Okay so I'm sure I'm just screwing up something simple, but I've had a serious problem trying to host a game for my friends. Every time I host they get a server not responding (And when they host, it's the same deal when anyone tries to join them). I've searched google and the forums for any help, and all the suggestions (sv_lan 0 and a map change, using hamachi and stuff like that) all did not work. The games do not show up in the server listings in either case. And I made sure my firewall was off, and I'm not using a router so I don't think it'd be my NAT type.

Any suggestions?