Can't load minecraft world

I have created a world in 1.5 my first and when I leave it was very good but when I go in game with this world it can't be loaded and 1-2 min later the game redirect me on the title screen. I have a video in attachments.
In the world I use redstone comparator, 2 timer, 2 dropper and many hopper.
Sorry for english i'm french