Re: Mental Ray Fatal Error????

Its possibly a translation error. When you render with mental ray maya packages up the scene and feeds it to mental ray in a format that mental ray understands. This is called translation. I bet somethinig in the hair object is breaking during translation and causing instability. If it is just the hair at least you know what is broken. As to why, thats harder to answer.

I suggest monitoring the amount of memory used when trying to render. If you see any big spikes it could be that you're running out of memory.

You can also set the mental ray translation verbosity to level 4 5 or 6 and it will spit out far more information, hopefully helping you pin-point the reason.

Finally, you can export the hair out to a separate maya file and render the hair alone. Debuging the problem alone is much easier than with a ton of things in your scene.