A lot of us is dealing with Black Screen onSceneLoad android issue after upgrading to unity 4.3.
See http://forum.unity3d.com/threads/215426-Unity-4-3-After-upgrading-to-4-3-the-native-android-plugin-stops-working
Most of our users reported the issue for android JB 4.2 and above.
Some of them solved the issue by downgrading JB to 4.1.