Kate Lenthall
Comments
Hugely seconding this issue. In a new world I made to try out with the current snapshot, I ended up accumulating a ton of stuff, and wound up with a horse, and a donkey and three mules to carry everything. After flying around to find a place I wanted to take all my stuff and settle down to build, I set off on foot with my animals, and immediately ran into trouble with the leads breaking. I ended up having to stop halfway there to leave three of them tied to a post while I continued on with the other two, and even then I still had leads breaking. It does seem to happen when they stop to graze while I'm still moving, and if I pass through an area smaller than their perceived hitbox size. A trip that I was hoping would take me ten, maybe fifteen minutes, ended up taking a little over a half hour, because I kept having to walk backwards or stop and look back to do a headcount. Going through a forested area was agony. I've seen it stated in other bug reports that the leads don't have infinite strength, but this is ridiculous.
So far in one world I've lost three baby horses to this problem. One time it happened on the single hay bale I had near the baby and parents, who were all tied to the same post. Another time I had the parents in a small fenced-in area attached to a house (area was probably 5x5 or so) and the baby, once it spawned, got stuck in the side of the house and died. It's pretty annoying, since Golden Apples aren't super easy to come by/make.
I'm having this problem as well, with unmodded 1.6 snapshot, and I already tried updating my lwjgl. I'm on a Mac, and holding Control while clicking on a stack of any item does not make it split evenly or allow me to place single items in inventory/crafting slots. Makes it very difficult to craft.
I've seen randomly spawned horses suffocate in blocks when there isn't enough space for them, like when a group spawns near a hill; this has been a problem since horses were introduced (and wasn't a problem when using Mo' Creatures" and has continued to be a problem all the way through into 1.8.