Have you tried connectin the ps3 using the ethernet cable rather than wireless?
All the problems i have seen with connection problems are either to do with NAT type 2 and 3 or people using WEP when some should be using WAP.
Not much help i know, but there are quite a few threads on the forums regarding issues like yours.
Ring Sony ps3 helpline or your broadband tech support, thats what they are there for
