TVOutManager working on Simulator, but not on a device?

I am trying to project my iPhone app on an external display. I tried TVOutManager, It works perfect on开发者_StackOverflow社区 the simulator (I turned on the TV Out Option, and have tested iOS from 4.0 to 4.3). However, when I install the app on my iPhone4, it doesn't work neither on an external display nor on a TV. Am I missing something or there are some special requirements for the cable or accessory?

#import "TVOutManager.h"
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions { 
    [[TVOutManager sharedInstance] startTVOut];
    .....
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
    [[TVOutManager sharedInstance] startTVOut];
}

Thanks

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Make sure to use a high quality VGA-cable, or a short one. Short one is better of course.

Trick to make it work, when it's not:

1. Connect projector cable
2. Open app
3. All well? Stop and pet your back, if not continue:
4. Kill the application with a double-home-button-death-tap
5. Restart the application (with the cable still connected)

This usually solves the problem for us, step 3-5 might need some iterations.