| Well, it may be just your ISP. Basically, you're loosing too may packets. See, if your ISP has a forum, there may be some people who had issues with PS3 and have an answer.
With your setup, I'm not fully clear with the modem. Do have you have of those router-modem combo things? If so, you'll need to be careful about double NATing. If it is, I would have D-Link as an access point only, meaning, turn off any NATing in the router. Just assign the router an IP outside the DHCP range in the modem; you can do the same thing with the PS3 if need for things such as port pin-holes or DMZ.
Unfortunately, or fortunately depending on one's view, I haven't used DSL, so I'm not familiar with how it connects or using PPPoE connections. I have no clue what the other connection is. But you should only be getting one IP from your ISP; I assume you're using a dynamic service and not a static IP (it's usually pretty expensive to get a static IP from your ISP). There's usually two DNS addresses (you may have to look them up. I can't only tell you how in linux). | 
