You need to poke around in Your router's config, either:
1: Set up NAT port forwarding on Your router for the PS3 - it's firewalled in this case.
2: ...or assign a static LAN IP address to it (by it's MAC address) & set that IP into the DMZ (De-Militarized Zone) - not firewalled in this case.
If You go with the first option, these are the ports to forward to the PS3 in the router:
UDP 3478 - 3479 (STUN; Simple Traversal of UDP through NATs)
UDP 3658 (Playstation Network)
Either option should take care of it
