I am having the same problem but my network was working fine for like 1 year and then this comes up when i try sign in, and this is the original account i created as like my master account like this is no sub account so like **bleep** is going on? can anybody help me?
Guys, I have a PSP but I think this might sort your problem out...
I just had the same issue while trying to sign in to play Resistance Retribution multiplayer. It so happens that PlayStation has revised their policies and want us to accept the new regulations. I signed in to my PlayStation network account from my PSP and it prompted me to read the user agreement and accept it again. I then signed out and re-signed in and everything worked just fine. In fact, when I logged into my PSN account through my computer, it took me straight to the new regulations. So I believe you may be able to do it over the computer as well. I think this didn't happen to everyone right away because it was probably rolled out in stages in different countries. I'm based in UK and had this problem only today.
I hope this helps and if it's not what you're experiencing, then apologies. You might just wanna ring Sony.