Spiders run too fast, at least for the first minutes after world reload, and may cause crash

Just after I had opened my world in 14w06a, spiders ran incredible fast. It happened for a few times. Probably it happened only with the spiders that spawned before the update. I spawned new spiders and switched to survival during nighttime the bug didn't happened.

Video: http://www.youtube.com/watch?v=SjUzLEFbyBg