I’m having trouble with some cameras in my scene. Every so often one of the vray cameras that i’d been using suddenly stops rendering. The rendering renders black. Sometimes I get A fov is to small error, sometimes not. I then merge that same camera from a previously saved scene and all is well. Any ideas why this would be.
What did you change on the camera from its default settings? Also did you apply any modifiers like Camera Correction? If you did, try taking it off and try putting settings back to default, see what happens.
Maybe u have objects in front of camera that are visible as boxes. Or ur lights get dark or something simmilar?
Bottom line there might be scene in bug that u keep merging to new scenes.
Other than that try creating new camera - aliging it and linking it to other camera see if that helps…
I stumbled on the same problem. In my case it was indeed some sort of a camera corruption. Recreating exactly the same camera with identical parameters and position solved the problem. I also had the “ccamera FOV is too small” error, while the FOV was 24mm, which is more than common
Oh man 2011 
Well done gold digger!
Yeah, so what ? I dug this because there was no confirmation of the solution.
Not saying its bad! 
Just nice to see old stuff surface up from time to time 
Ok ! no problem.
And thank you, since you provide the solution that saved me some precious time !