Hello,
I tested your cube and its full or errors (Object i tested is on this link
http://supervision2.filnet.fr/froggy/ftp/obj/c1.3ds).
Major Problems
- It is setup to "editable mesh" when it should be setup as "editable poly".
- Your 'cube' have 14 vertices, how come ? A normal cube should have onle 8 vertices (one for each corners).
Minor Problems
- Its not a cube, more a rectangle :p
- No texture attribued
- Rendering method is phong, i'll rather go with blinn