Saving out IR maps CRASH

Getting this error…

// Error: line 1: Exception : Irradiance map thread //

Any ideas?
We are rendering out IR maps every 3rd frame for camera animation on a large village scene.

Many thanks
Maya 2015 Beta 3 nightly

Have you tried older or newer builds, or even V-Ray 3 final?
Can you share a scene, so we can reproduce it?