my app stops after running...(in Console) and gives "debugged is not being run."?

After running my app, I am getting following problem, can any one has idea, what is problem

This problem is only in my iphone 4g, not in 3g,,,

Error launching remo开发者_C百科te program: failed to get the task for process 224.

Error launching remote program: failed to get the task for process 224.

The program being debugged is not being run.

The program being debugged is not being run.

---

This has happened to me lots of times, but not in a while. I believe it happens because xcode believes that the app is installed on the phone when it isn't. An easy way to solve it is to alter a source file (add/remove whitespace), so that xcode recompiles the app and transfers it to the phone. I believe that's how I used to solve it.