Problems connecting my PS Vita to internet with my router

Im trying to connect my PS Vita to internet with my router, but Im having lot of trouble. The connection to the router seems to work ok, but internet is not working. When I run the "Internet Connection Test", I get this:

Obtain IP Address    Successful

Internet Connection  Successful

PSN Sign-in          Failed

Error code : c2-11003-5

The WWW Browser doesnt work either. What am I missing? My Android phone, my laptop and all the other devices Ive connected to the router worked alright out of the box.