My iPhone 3GS won't rotate into landscape, My iPhone 3GS won't rotate into landscape

When I try to use the rotate into landscape feature in camera, safari, email, etc it won't work, but if an app requires it, it will default to it, but it won't work at any other point. I have read other forum posts, and downloaded the labyrinth le app, and I can tilt in all directions. I have checked the lock in portrait option on the slide menu when u double tap the home button, and it is unlocked. I have also tried hard shutting it down. I am at a complete loss. I have even gone back and deleted the app I downloaded the night it started acting up. Please help! Thanks!