Need help using Facebook SDK for windows phone

Hello everyone,
I developing a simple game that using Facebook SDK for Windows phone.
I read from this link: http://facebooksdk.net/docs/phone/config/
Everything is fine but when I add this code to InitializePhoneApplication(), the game stops working with no reason:

RootFrame.UriMapper = new FacebookUriMapper();

If I remove this line, no error but no callback when player authenticated.

Does anyone have a same problem? Please help me to fix it! Thank you so much.

p/s: Sorry for my bad English!