I already tried rearranging the modifiers, but the same problem exists. Does it have to do with my using Cycles instead of Blender Render?
Try this one test and see what happens: place the surface subdivision modifier above skin modifier. Sometimes, modifiers clash with each other, so you have to test them by moving them up and down within the panel. If that does not work, try moving mirrior modifier down. If nothing, try applying surface subdivision. If that fails, I hope somebody else will have a solution.