Error with movement.

I am currently creating a game in slick, I am also making graphics for it, But i seem to have a problem, When i try to hit my left/right arrow keys the player doesn’t move, Up and down arrow keys work, If you were to hit down/right/up or down/left/up keys the player moves straight.

My Play.java code, Contains the movement.:http://pastebin.java-gaming.org/3cf6e423b1c15