Command blocks does not execute command when powered.

When i type a command into a command block and power it the command block does not execute the command. All is says is " - " . I tryed to use 3 different commands.
1: /tp @p -110 57 0
2: /tp @p -110 73 0
3: /say hi
None of these commands are working in the command blocks in my world.
This is really a problem because I am making an adventure map.
Can you please investagate this problem as soon as possible.

Many Thanks