multiple plugins Unity 4.1.2

multiple plugins Unity 4.1.2

I want to use two plugins at the same time.They work perfect
individually.But when I use them both at the same time , one does not work
but another works or vice versa.
I have already read these links :
Cannot start activity on Android through Unity
http://forum.unity3d.com/threads/184960-Unable-to-start-activity-NullPointerException
http://forum.unity3d.com/threads/149089-Android-Plugin-multiple-Android-Activity-problems?p=1058651&viewfull=1#post1058651
but It still crashes.Giving me NullPointerException : Unable to
instantiate actvity component info.
I have declared activities in the AndroidManifest,But I dont know whats
wrong. I am getting null pointer exception at
super.Oncreate(saveInstanceState); after firing an intent.
Please help me out.I am stuck here.