Trouble rendering Array Modifier

Basicly I have a semicircle extruded, rotated, and pushed into a rectangle who itself is under the spell of an array modifier. The problem is that at rendering I always get this sort of “line” or “seam” that gets through like in the following picture. Anyone knows how to stop it from displaying and start displaying it without a seam?
http://i291.photobucket.com/albums/ll316/tegramon/test.jpg

The lines look to be where the faces from your semi circle overlap the faces of the rectangle. My advice would be to connect the two shapes into one mesh.

Well, they are three objects, one octogonal base, a rectangle and the semicircle. The rectangle and the semicircle are arrayed. How do I combine ALL objects so that the array modifier is gone, and I would have only one single mesh without any modifieres at all?

If you want to make the array duplicates real, click the Apply button on the Array modifier. you can merge multiple object, by selecting all of the objects and pressing Ctrl-J. However, you may still need to actual merge the vertices of each shape into the other. That is, connect the verts at the bottom of the semicircle to the top of the rectangle, connect the rectangle to the base, so that they are all one continuous mesh.