Tree bark is always black, but I'm pretty sure I didn't do anything wrong

So I'm trying to use the trees part of the terrain editor. I imported the terrain assets package from unity3d.com, and the trees are definitely in a folder tagged "Ambient Occlusion", and their bark and leaf materials are set to their defaults, Soft Occlusion Bark and Soft Occlusion Leaves.

But even still, when I add them as trees to use on my terrain, the leaves look okay (but are not effected by light), and the bark is always pitch black no matter what, and unaffected by light sources. Also, the bark texture preview (the circle next to the material in the inspector when I look at the tree in my assets) is pitch black as well.

Am I doing something wrong?

I figured it out... it was because I was leaving the scene vertex lit. Apparently the terrain editor trees need you to switch to lightmap before they get lit :)

I have had the same problem and the answer isn't pretty. A way to fix this is to create a Layer in which you put the black objects. Keep creating lights that only illuminate that layer and blow out their intensity. Eventually the black objects will look normal.