Firstly are you connected Via Wireless or a Cable to your router.
If Wireless go to the network options on your PS3 Main menu and run the Internet connection check what speed does this report, if its below 1mb then you may have an issue playing.
Check that you are getting the correct speed from your ISP I dont know if your are ADSL or Cable.
Set your UPnP to be on this affects VOIP and other stuff
Power off your router and leave it for 5 minutes then power it up again
If you are Wireless get a cable and plug it into the PS3 and Router and try direct wired does this make a difference.
When you have tryed the above let me know via this page and I will see if I can think of anything else
well my post says i have a wired connection to my router(netgear) and its a ethernet cable but i have tried messing with UPnP settings with no help
