iOS Question Problem with simulator

Hi everyone,
as you may have guessed, I'm new in the B4I field.

With B4I rev 5.50, I tried to run the "Hello World" program.
the application is compiled correctly.



Selecting "Tools-Simulator" and then F5 (Run):
the simulator starts working and then stops immediately. The following list of errors appears:

Error occurred on line: 7 (Main)
Unknown command: 0
Stack Trace: (
CoreFoundation __exceptionPreprocess + 331
libobjc.A.dylib objc_exception_throw + 48
CoreFoundation +[NSException raise:format:] + 197
B4i Example -[B4IShell raiseEventImpl:method:args::] + 2258
B4i Example -[B4IShellBI raiseEvent:eventarams:] + 1625
B4i Example -[B4IStaticModule initializeModule] + 434
B4i Example -[b4i_main initializeStaticModules] + 67
B4i Example -[B4IShellBI raiseEvent:eventarams:] + 232
B4i Example __33-[B4I raiseUIEvent:eventarams:]_block_invoke + 50
libdispatch.dylib _dispatch_call_block_and_release + 12
libdispatch.dylib _dispatch_client_callout + 8
libdispatch.dylib _dispatch_main_queue_callback_4CF + 1276
CoreFoundation __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
CoreFoundation __CFRunLoopRun + 2310
CoreFoundation CFRunLoopRunSpecific + 626
GraphicsServices GSEventRunModal + 65
UIKitCore UIApplicationMain + 140
B4i Example main + 112
libdyld.dylib start + 1
)
Application_Start




Selecting "Tools-Build Server-Build Release App:
all works well (but every time I have to uninstall and reinstall the app to try a change)



where am I wrong.
What could be the problem?
Thank you all.