I've had this problem a number of times and nearly every time it results in me having to abandon a project and start anew simply because I can't work out what is going wrong. I am using Lionel's wonderful export script to export from Blender to Octane (still the best way to interface the two programs).
I am getting the following error.
Anyone got an idea? Before anyone asks, the render has exported and rendered a number of times. I can't remember what I did to the model to cause it to do this but it is obviously objecting to something about my .blend.
Cheers