what's your FW number?
if you're on the most recent, you can check your networks settings on the PS3 and maybe post results (i.e. if there's any failures, don't post personal information!).
lastly, plug your PS3 directly into your modem. if you don't encounter any problems, it's the router. if you still can't sign into PSN... i don't know what else i can tell you
it has nothing to do with the internet settings. ThePSN went down last nightfor many people and is still not up and working. it died sometime around 7/8 PM EST last night (3rd). there are already at east 4 seperate discussion threads in the support area about this also. and so far, not one single word from sony.