multiple plugins Unity 4.1.2

Question

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.