Works perfectly with my PS3.
I have been using this same DGL-4100 router with my PS3 since launch (I have a 20GB PS3 from November 2006). It has always worked exceptionally well. I am currently on firmware 1.8, which is no longer available, but it worked fine on 1.7 as well.
My current setup is as follows:
Oceanic/Time Warner cable modem -> WAN (CAT6)
TrendNET TEW-637AP wireless-N access point -> Port-1 (CAT6)
D-Link DGS-2208 gigabit switch -> Port-4 (CAT6)
And I have 4 computers and my PS3 all hooked to the switch (all CAT6).
Originally I had 3 computers and the PS3 all wired directly to the router with CAT5e and that worked great too. I can't imagine what your problem could be. It's definitely not a compatibility issue with the PS3. My DGL4100 has always worked flawlessly with my PS3, even through several firmware revisions (of both the router & PS3).
I'd say try another Ethernet cable, and/or other ports as suggested above.
When you are trying to set up your PS3 are you going to Settings > Network Settings > Internet Connection Settings and then choosing Easy?
If that doesn't help then we will need more info, like who is your ISP (company, cable or DSL) and what kind of gateway are you connected to (modem only or combo-modem+router, make, model)?