Camera app crashing on Nexus i9250 Android 4.2.1

I just bought a i9250 Nexus, and the system proposed to upgrade to newer version 4.2.1 (it is not a rooted phone. It is an unblocked UK phone) I played with the new phone and after a couple of days I did upgrade it. Now the camera is not working. When I try to use the camera, it calls the application and before I can see any image from camera, it says "Unfortunately the GALLERY has stopped" How can I downgrade to previous version? (The phone is not rooted) Or, does anybody knows how to fix it? or anything that I can try to bring the camera back to action?