The first thing I would check would be your file paths.
It's also possible that another program had on of your files "in use" or "locked", but here is how things look to me:
This looks like you have a missing texture for your clip:
http://s17.photobucket.com/albums/b74/Desert-Rat/Oblivionmods/?action=view¤t=Untitled-2copy2.jpg
This one looks fine:
http://s17.photobucket.com/albums/b74/Desert-Rat/Oblivionmods/?action=view¤t=Untitled-1copy4.jpg
This one is missing the "assaultCarbine" that was partially visible in the Model field, and also has "meshes" in the path which I normally do not see there:
http://s17.photobucket.com/albums/b74/Desert-Rat/Oblivionmods/?action=view¤t=Untitled-2copy3.jpg
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When you browse to your .nif and select it, does this happen again? If so, what happens if you select a different .nif?
If it's your .nif, and if fixing the missing texture in your .nif does not make the problem go away, I would start wondering about required nif structure, but I am out of my depth if that is your issue.