Transparent cylinders?

[angeljs]

I'm using Wings 3D 1.5.2 and am encountering a problem I've not had before. I'm a relatively new user, but have been using this software to create meshes for the Sims 2.

For some reason, after I've used Tesselate/Triangulate, then mapped the mesh in UVMapper Pro, and then import it back into Wings, the cylinders are all transparent:


Any help would be appreciated. Thanks.