Running android app on version 4.0.3 crash?

Hello. I have created my first application for anroid in unity. It works fine on my phone, which is version 4.4.2 but when my father tries to run my application on his version 4.0.3 the phone just shuts down! I tried it on another phone running version 4.0.3 an its the same :( I am a bit frustrated, because it worked fine on his phone until i integrated chartboost. I tried to delete chartboost but it the phone still shuts down.. Anybody who have the same problem or is possible to help?