Cogmin

Hi, if i could get a respose ASAP, that would be great. My problem is, I am following a Minecraft Modding Tutorial for Minecraft 1.7.2, and it has been very rewarding so far. Recently, I followed an Ore video, in which the guy explained how to make Ore Generation. I followed his steps exactly, and while he doesnt get an error, I DO! :'( Minecraft WILL launch, but when i load a world, it crashes! PLEASE HELP