I had just downloaded and installed the 13w02a snapshot and started to play.
Everything was fine until i went in to a world. All of the textures (except for chests, ender chests, etc) had gone all wierd, for instance, dirt was completely white, grass had a green top with no detail and a white side and bottom, leaves were completely green.
I will attach some pics

I also got 2 pictures on my desktop which will be attached.