ACS Push crashes my App

Hi folks,

I have developed a App some time ago and now I decided to use ACS Push Notification but something strange is happening.

If I send the Push when the App is opened, it runs fine. I get the Push normally. But if close the App and the send the Push, I get the message "App stoped" and cannot get the Push.

Have any of you ever seen anything like it? Thanks in advance!