When I place a command block down, give it a valid command (I checked, and by no means should it not work), and try to power it with a button, pressure plate, powered redstone dust, etc, it will not function. There are no problems with the command. The problem appears to be due to the redstone signal not being existent. However, it appears to only not be existent in certain areas, since a similar teleport command block works near the center of the world. I have not tested to see if redstone can be powered in this area (the center of the world), however a button press against the command block works fine, there.
Iron doors don't work, either.
I have exited the world twice, and it still will not work.

EDIT:
More research has been done, and it appears to not be working at the edge of the world. Or rather anywhere within two chucks (32 blocks) of the world edge. This error occurred on the old world type.