Basically, the best solution is to ensure that Universal Plug and Play is enabled on the router, which will enabled to PS3 to set up it's own port forwarding.
Failing that, you need to forward the ports listed in
http://boardsus.playstation.com/play...hread.id=60067
For instructions on port forwarding, look up your router on
http://www.portforward.com/
I would not, under any circumstances, recommend you disable the firewall. You may solve your problem, but you will open your network up to possible intrusion, would could lead to a lot of other problems.
Welcome to the forum, BTW.