Problem export a unity game to android

I have recently finished to create my first game in unity 4.6 and it works well inside of unity. Now I want to export my game on android platform. So I follow the official tutorial in the unity website to do it: I download the JDK and the SDK and I download the required things with the SDK. After that i build the project step by step with the official tutorial but also other videos that allowed me to undrstand better this manipulation. After that i get my APK and I instaled it and then everything seems to work fine. When I launch my aplication I arrive on the main menus and I can "click" on the buttons and it load others scenes. But when i arrive on these others scenes the buttons stop working and I cannot do anything except quit the app manually with the home button of my phone.

Others informations : I am using a nexus 5. I am using windows 8. Evry button in my game are made with the UIbuttons.

What i have tried : Use an other device : my tablet but it doesn't work. Reinstalling the SDK and JDK but it doesen't work too. The unity remote4 and it works fine. Export my game in .exe and it works fine too.

So with tese differents attempt I pretend that the problem came from the compilation. But I don't know what to do now.

This problem is driving me crazy. Please help if you can.

And sorry for my bad english