I modeled two pieces individually so I would fill my screen with more than one piece. I then tried to open each piece and then tiled them side by side and I can get either piece into the other piece's viewport but I can't get them lined up no matter what I do. I also tried the insert block command but I am coming up short trying to assemble the pieces together. I also couldn't get them to line up right!!
Dear 03 SB FX4,
Hard to say without more information, but my first guess would be that you are using an incorrect base point as anchor for your block.
Also, you may be using the incorrect esnap option for your operation?