That was happening to me last week, i fixed it.
Perhaps this is too easy, but this was my problem:
-Go to your home screen and keep your phone in portrait mode.
-Slide down the status bar and make sure screen rotation is activated.
-Open up your browser and hit the settings button (button all the way to the left)
-Go to More > Settings > and check or uncheck "Landscape View Only".
Plan B is to shutdown your phone for 10 seconds and reboot...