Attached Link: http://www.3dmenagerie.com/goodies/tut/abng.htm

There's all kinds of things that can go wrong, but it's most likely a reversed normals problem. Most meshes have only a single side that looks solid from one angle and is invisible in the 180 degree reversed angle. A lot of objects are created in other programs by modeling half the object and flipping it to create the symmetrical other half. That often leaves reversed polygons.

A quick, not perfect fix is to use the grouping tool in a broad fashion to quickly get all the visible normals forward. The linked tutorial provides a better means of doing the job correctly. The below technique only works for one view and has to be repeated every time the camera angle changes because that change shows other reversed normals.

Once in the Group Editor:
New Group tab
Click in the Preview Window and draw a rectangle around the entire object
Click Remove All
Click Reverse Group Normals

That will correct all the reversed normals for that one view. The downside of this broad approach is that all the good normals, that currently cannot be seen, are reversed.

Another better fix is to click the left and right arrows by the group name (<< and >>) to see if some of the grouped parts of the mesh are totally reversed and reverse just the bad ones.  This won't work if there are bad triangles within a group. 

My visual indexes of Poser content are at http://www.sharecg.com/pf/rgagnon