As it turns out, Sony updated their Terms of Service which had to be accepted on their website. Users on the Vita weren't informed of the new TOS though so people had to find out how to fix it on their own. It really is a big fuck up from Sony.
Here are some ways to fix it:
Accept new TOS.
Seems to fix it.
log in here http://eu.playstation.com/
and accept the new TOS
log in here https://account.sonyentertainmentnet...isplay.action?
then everything is fine
I fixed it by going
and then starting any PSN-reliant application. The new TOS pops right up and you can accept it then and there.