Several crashes with loss of features

Every time Minecraft crashes (and it actually arrive really often since 1.1.0), I lose dogs, boats, horses, …

(Most of the time, chrashes arrive when I go far from my home. Maybe a problem with the chunks' generation?)

After the crash, when I come back in the world, the horse I were on just vanished. Same thing for dogs, that are not findable.

Thanks for help