So having trouble with skeleton mesh inside of UE4, when i try to apply a material to a instance of the mesh inside of UE4 it makes all the other elements disappear. below is a set of images to help and describe the problem. The first image is what it looks like before I drag and drop the material.
If this particular issue is a blocker for you then you will want to upgrade to 4.6.1 as the fix for the issue is implemented in that version. If however, you are ok with setting the materials through the Skeletal Mesh Editor or via a blueprint components panel, and you can work around the issue for now and are happy with your projects progress then I would not update.