Inputting Models into Halo 2.

[mrtikki2]

Hey, I recently made a pistol in 3ds max 7. Using 3ds max, I saved it as magnum.3ds. I opened up magnum.3ds in milkshape, and exported it as magnum.obj. I opened up shared.map using dark matter and exported the magnum model. I got 7 files.

magnum.gun.base[0][0][0].obj
magnum.gun.base[0][0][1].obj
magnum.gun.base[0][0][3].obj
magnum.info
magnum.mtl
magnum.jpg
magnum_lod.jpg

I Deleted magnum.gun.base[0][0][3].obj and renamed magnum.obj (the one i made) to magnum.gun.base[0][0][3].obj. Using dark matter, i click import..and selected the folder, and I got an error saying

Object reference not set to an instance of an object

What did i do wrong?