I'm having one of those black-screen problems with the Unity video sample when running on a Samsung Galaxy S2.
I'm using the videoplayback-3-0-10 Unity package/sample in Unity 4.6.1, on a Samsung GT-I9100 running Android version 4.0.4.
The sample works fine on iOS devices & on a Samsung Galaxy S5. I've also tried some of the suggested solutions to common black-screen problems without any luck.
I can't see anything in Logcat that hints at a problem either.
Has anyone else experienced this issue?