sorry, inturperated it the wrong way . just re read it and do what smash said, check it and check it again, And the first point of call, you soldering. If your soldering has created a short fix them. What type of board are you using. Strip board or the type of board featured in the $50 robot tutorial.
Either way get an extremly sharp knife and run it between each row to seperate the solder before you start to resolder when it may not be needed.
And try not to cut corners when you are debugging, it will only cause problems further down the track.