I ran into an issue where the camera was showing a black screen on a Nexus 10, but working fine on a Nexus 4. This happened on several different apps that had already worked previously on the 10. A restart fixed the problem.
I unfortunately did not try another camera app to see if the camera itself was stuck.
I'm running Unity 4.3.3f1 and vuforia 2.8.7
Am also facing the same issue. camera is off and showing black screen.
This is not every time. it is happening 20-30% of chance.
I have created a new post. please refer for total details : https://developer.vuforia.com/forum/device-support/black-screen-ios-devices-camera-mode
Any quick fix solution would be appreciated we are quite in a hurry!!!
Thank you.