No material on objects in linked group? I took a few meshes and armatures, and placed it in a group. Then I opened a new blend and linked the group. Now all materials are gray, and it looks black on rendering.

I tried to add a proxy, and that works for animating the armature, but there is still no material.

Why is that? When I tried the same thing with a simple red box, it works. However I can see the materials used in the linked file when I look at materials for another object. However if I try to use them on the default cube, it doesn't seem to work.

Any help appreciated!
Change the render engine to the same as the source file, in this case Cycles, instead of Blender Render which is the default for new scenes. (Thanks to Duarte Farrajota Ramos)