The way I stopped all vray conversion crashes :
1, Convert all VRay2SidedMtl to normal material (drag front material to top level)
2, Ensure Translucency type is set to None (ie. not Hard Wax, Soft Wax or Hybrid)
3, Ensure Refract colour is completely black. .. . otherwise it becomes a stupid specular material.
Cheers,
M.