anyone having the problems with mirrored instances coming out black,
(mainly when instanciate is on)
just check force 2 sided and its fixed 
same thing if you have normals faced the wrong way and rendering black.
It was just by chance that we found this, considering that vray renders everything 2 sided anyway, it surprised us that forcing 2 sided fixes this hehe
Thanks for this tip. Using instances renders are faaaaster, and now i can use it 
Unfortunnately, this isn’t fixed that way.
You’ll get messed up UVs and a bit darker render for the instanced-mirrored object when the bug occurs (depends on the lighting ambiance though).
You should try to “reset x-form” and then apply a normal modifier with “unify” checked & “flip” unchecked.
Of course, if it’s working on your side, don’t do anything. 
curious that this bug was not present in the earlier builds of Vray. i just noticed that rendering a scene with the latest build the bug appears but i have a rendering of the same object from an early build (1.09.01a) and it looks fine there.
joel
I’ve had this bug for a long long time.