The Playstation Network will be going through routine maintenance January 19 (today) from 8 am to 9 pm PST. During that time you will not be able to access the following features:
PlayStation Store on PS3, PSP, and Media Go.
PlayStation Network Account Management.
PlayStation Network Account Registration.
Music Unlimited & Video Unlimited services
It has also been stated that you will not be able to sign in to PlayStation Network from us.playstation.com. Users who were already signed in at the start of maintenance should be able to continue their online session but those who have not signed in recently may be met with the maintenance notification page.