Can you please provide more details? What exactly did you change, and what specifically do you mean by the tiles aren't opening?
If you mean that you changed your main page's Xaml and now the app won't start up then there is probably something wrong with the Xaml. Running it under the debugger may give a hint as to where the failure is. Obviously, if you only made a small change then
that would be a good place to start looking.
--Rob
