I think I have run into a bug in Cycles (I have Blender 2.76)
It is a very simple scene with almost nothing, 1 camera and one polygon. Camera is looking away from polygon but it still show on front of it.
I cut this down from a bugger anim with lots of stuff and at 9000 frame problems started showing up. So I cut it down to the barest of minimum. Strangely enough the realtime display render worked fine - the F12 and Ctrl-F12 produced a different result.
Attachments
KOE.blend (521 KB)