I changed something, the back of faces does not render in the viewport and I also cant select the back of faces. Also even with a two sided material the back of faces is not lit. Any help would be awesome, thanks.

It sounds like backface cull which turns off the backface of your object.

To enable/disable this option right-click the object and under the object properties there is a checkbox for backface cull.

website: http://www.all3dmax.com

No its not that, its like a general setting of some sort, thanks for the response though.

Have you turned on “Ignore Backfacing” on the Selection rollout?

Back faces not rendering is correct - they shouldn’t. They can be made to, but that is a “hack” - polygons are single sided entities so if the object is modelled correctly, the camera should never be able to “see” a backface.

Max 4.2 through 2013.
XP-64 (SP2)
NVidia 9800GTX-512 (Driver 266.58).
Core 2 Quad Q6600 2.4GHz, 8Gb Ram, DX9.0c.