Hi to everyone!

i need an help, i've imported from Sketchup an .OBJ (first screenshot) of a boat in Poser 11 (second screenshot) and i don't know why inside the hull, rounded in red, the walls became invisible and we see through them. Only the internal walls, as you can see the externals remain. And this happen even if i import it in .FBX, 3DS, etc.

Is the problem the file itself of Sketchup? or is the importing in Poser? can anyone help me?

Thank you!