I am currently testing the new embree (1.1 beta) in my renderer. I am really impressed by the build speeds, but I keep getting one assert fail in one of my test scenes.
I reproduced it in your embree desktop application, it always happens in one fairly big scene (7M tris) with default settings (BVH4, triangle4).
It is line 81 in bvh4_builder.cpp: assert(!iter);
I've obtained permission from the author to give you the scene for debugging purposes, if you keep it confidential. If you want it, give me an email address where should it be delivered.