My minecraft will not work on the new update of 1.6 and 1.6.2. I have a Mac OS X Version 10.5.8

What happens is when I try to play 1.6 or 1.6.2 my screen goes black or white. I can play, but I need to go onto the new launcher, create a new 'Profile' on 1.5.2 and play on that, but I would enjoy using horses and everything new on 1.6