My Iphone sdk aspen simulator not running apps

Hello all!
I have a mac os 10.5.5 and iphone sdk 3.1 beta running on intel. Problem is that i can build apps on xcode but when i run the same app, it doesnt run on the aspen simulator. It only shows the black screen and then returns to main menu.

Error on xcode is:
Error from debugger: Failed to launch simulated application. See console.

And when i see the console, it says something abt not loading the simulated app because it could not find SpringBoard (bootstrap_look_up error).

Please Help!