Might be a silly question, but did you make sure the black pin was all the way up (turn the clip the direction of the arrow and pull up) before trying to get the white plastic clips back together again? Had a similar problem where one of the head bits got bent, but managed to get it all back into shape without too much effort once the black pin was all the way out again. If you do try and fit it, squeeze the head and push it through the mobo hole first before doing the other ones...