how to fix java exclamation point when loading a game

hi so i just got my macbook out of repair because of my hardrive failiong and they installed a new one and i had no back up of my operating system so they put it in for me. My software is on 10.6.8 and i have java 1.6.0_51-b11-457. Know when i try to run a java requird website or game it loads and then stops and then comes up with java cup but with a red exclimation point. Can anyone help me with this please?