3ds Max 9 Flip -option help needed!

[DaHandy]

I started to make a HaloCE level with 3ds Max 9 with this: http://www.halomods.com/tutorials/Mappi ... 02-3ds.rar tutorial (it has been created with 3ds Max 5).
In the tutorial, he uses a "flip" option. When he uses it, the skybox goes like that he can see inside it. When I use that same option in 3ds Max 9, the box just goes black.
What is the problem?

Sorry for my bad english...

[SPARTAN04]

did you apply a black texture to it or something? did you select all of the faces and then at the surface properties tab thing did you press flip?

[Paradox621]

I started to make a HaloCE level with 3ds Max 9 with this: http://www.halomods.com/tutorials/Mappi ... 02-3ds.rar tutorial (it has been created with 3ds Max 5).
In the tutorial, he uses a "flip" option. When he uses it, the skybox goes like that he can see inside it. When I use that same option in 3ds Max 9, the box just goes black.
What is the problem?

Sorry for my bad english...

Select the object, right click it, select "Object Properties", and check "Backface Cull".