There are literally loads of reasons why this could happen. The info I asked for above will give a clue as to what the problem might be. If you hit the F8 key as Chameleon starts you will be taken to the Chameleon boot screen. Type - v here and hit return. This will start your computer in verbose mode and a load of white writing will flash by. It will eventually stop and say kernel panic and give the reason. Note this down and post it. This may or may not help in diagnosing your problem.