"If you are experiencing problems with a wired (Ethernet) network connection on the PS3, try these troubleshooting options:
Turn off (unplug) ALL of your network devices and equipment making sure all lights on the modems has turned off, including any wireless access points, routers, Voice Over IP (VOIP) modems, and broadband modems for two (2) full minutes. Certain VOIP modems (where your telephone is connected to your modem) may have a battery installed. You will need to remove the battery in order for the modem to be completely turned off. Check with your VoiP provider before removing the back-up battery."
Have you attempted this (or any of PlayStation's support suggestions) yet?
Edit; this may also be helpful: http://faq.en.playstation.com/app/an...710102-mean%3F