This is how you need to set up a wired ps3
.1. ethernet cable from Ps3 to port 3 of router
2 cable from port 4 of router to computer
3. cat cable from modem to router port labled internet
4. plug cable line to modem
5. plug in power source Done !
the router will automatically find the ip address for you
if ps3 is telling you that you have a dns error then all you have to do is go to the sign in and sign back in and accpt the new user agreement
I had DSL a long time ago... hated it because it was NOT an "always on" kind of cnnection, I HAD to use PPP. I quick skimmed the thread and didn't see anyone mention this... pretty sure the PS3 has provision for this. Not to mention the OP said a direct connection to his "modem" so those talking about having routers can;' possibly help (unless they know how this stuff works).
BIGGEST pressing need in Home... add "banish from my screen" to the BLOCK command