I assume those two code examples are placed in "Menu" and "Game" classes. Generally, your code shouldn't cause any problems, but I believe the issue is because "Game" is most likely the root class of Sparrow, which is retained by Sparrow (so it is never dealloced). That is probably why the Game scene still appears to be active.
If your code is like this:
[_viewController startWithRoot:[Game class] supportHighResolutions:YES doubleOnPad:YES];
I suggest you switch around the class structure and/or names, maybe something like this:
[_viewController startWithRoot:[Main class] supportHighResolutions:YES doubleOnPad:YES];
And inside the new "Main" class, you then initialize the "Menu" class, and handle all the scene switches there (such as between "Menu" and "Game").
Also, you can still use the "dealloc" methods in ARC to debug whether the classes are being dealloced or not:
- (void)dealloc {
NSLog(@"Game dealloced");
}