Photon Emission Problem

[marjanoczkowicz]

I am trying to render an interior scene in 3Ds Max 2015, with mrSun exterior lighting and ~10 interior photometric lights. I am using final gather with global illumination (photon emissions). Renderer set to NVIDIA mental ray. The scene was rendering fine initially, however after changing some geometry the render progress bar gets stuck on 81% photon emissions. I changed quite a bit in the scene prior to this problem so I'm not sure if my lights, GI settings or materials are the reason for this sudden problem. Any help would be greatly appreciated.