Ok I suspected huge amount of recurse in scene and render just lost with calculation for that. It happen sometimes when you not limit recurse. I would like to see image. Also I can help you with limits for recurse: put this in all Nodes (It is all ready in Eclipse package)
So in Logic you have limitation for recurse - in this case for reflection. I use this limiter non stop. It increase speed rapidly in scenes with many reflection surfaces. So I do not allow render engine calculate reflection in reflection over three times because over 2 times you will not see different. For wooden floor for example I use ONLY ONE or maximum TWO!
Generally it can be situation when render engine "stuck" with calculation of reflection - it can be place when many high reflected surfaces are enough close each with not comfortable angle to camera. This is normal situation and I avoid it by this Logic function.

- sc_031.png (9.32 KiB) Viewed 25464 times
Add this for high reflected surfaces (metal) and tell me it helped or not.
Also problem can be completely somewhere else
