Okay.. i had this problem before. A while ago and i cant remember how i fixed it before i searched through 30 pages of threads and didnt find what i needed... Pretty much my model has another model of itself. So theres only 1 egde but at the end of the edge i can select 2 verts... I cant merg the verts, and its really bogging down my machine...

If i select the verts and move them The edges go with it. But theres another set of edges... But the edges i move have no polies between them they are just a shell. I think i went to some graph and deleted something. But i cant figure it out.. Any help?