Horses and Mules dont jump 1 block high while lead

So I was playing in a SERVER with a friend (pre release 3) and we were trying to bring some horses home with leads but they simply dont jump 1 high blocks so they just stay there (like if it was 2 high or a fence). I updated to pre release 4 and it still doesnt work.
I tried in singleplayer and it still doesnt work. It only affects horses and mules as far as I know. Chickens cows pigs and sheep are working fine!
Theres an attachment where u can see they dont follow just get stuck.