Creating a WP7 app is straightforward. Until you change the namespace.

Old hands will already know this, but if you change the (default wizard generated) namespace in a new WP7 application, you need to change it in several places in the code and the xaml.

One place that is not obvious, is that you have to change it in the application settings. If you do not, then when you try and debug your WP7 application, the emulator just starts and returns control to you. There are not any error, or informational messages in the output to tell you this.