I've been experiencing this for a whole freaking week, expecting to see it work again like it should but it wont.
Everytime I want to play online PSN logs me out. I can barely play one match in MW3 cuz in the next match I start lagging hard then get d/c from PSN. I already tried many solutions I found by googling and nothing. I can say that IT IS NOT my internet conection because I can play on my Xbox360 online without a problem. Now I want to know if its my account or something, I read somewhere that some people had their accounts glitched and couldnt log in till they made a new account, but I don't want to make another one because of my thropies and prestige levels on CoD -__- Now I know Activision servers are **bleep** but the thing is that I get d/c from PSN and not from Activision servers. I'd really appreciate some help with this :/ I might end up changing 100% to Xbox360 if this ridiculous problem persists (and i dont want to change cuz all my friends play on PS3 :l).
Try putting your PS3 on a Static IP Address. Also either enable DMZ or add ports to your router. heres a site for ports. Scroll down and find your games ports. I suggest not to enable DMZ and add Ports, Choose one (I suggest adding Ports). Another thing you can do is put your PS3 wired to the internet don't use wireless. Lastly check your internet speeds. Go here to test your speeds, You need atleast 10MBPS to not lag (I know this because of experience) etc..Hope this helps it did for me.