I don't understand the collision barriers in Blender. Could anyone tell me how they work or how to create a new one? The project I just did is worse then useless with the barrier I modified.

Arent the existing collision barriers sufficient? the editor_box thing (or whatever. the big blue box thing). You can always resize it in the cs and make it fit in whereever. Unless your trying to put an invisible collision component INTO another mesh. In which case ive got no idea

You need to make a mesh and have one segment be invisible (collision on, visiblity off). Avoid using transparency, instead hide it in your modeling program (right-click -> hide selected in most programs). If the exporter works right, it should become a CS-only collision wall.

You can also use NifSkope to hack the existing ones and either replace the geometry or take a peek at the flags they used.

The http://niftools.sourceforge.net/wiki/Blender/Collision illistrates exactly how to do this.