This error occurs because the edges that make the UVMap seams aren't split in the mesh. Basically, select the mesh (in this case head3), enter Edit Mode, switch to UV/Image Editor, press on the "Keep UV and edit mode mesh selection in sync" button (so to synchronize UV/Image Editor selection and mesh edge selection), select all the edges which contour the islands, then switch to 3D View, press Ctrl + E, and then D, and that will basically split all those edges in two - which means the vertex count will also increase, so be mindful of that if the mesh has a complex geometry (that is, if it's close to 1000 vertices). Hope this helps.