iPhone apps won't update
You might then need to log out of your account on your phone by tapping on your id in Settings > iTunes &amp; App Store and then log back in so as to 'refresh' the account on it.

If that doesn't fix it (if the account was disabled by iTunes Support then it might not) then contact iTunes Support : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page