I've got some very simple geometry (a cube with some extruded subdivisions). When I add a subsurf modifier to it these "wings" appear. They seem to be edges that connect vertices that weren't originally connected by edges. However, I can't select and/or delete them in any way.
How do I get rid of these?
I've checked the normals and they seem to be in order in the area that the wings appear in. Blender can't find any non-manifold geometry in the source.