So I went to download the minecraft 13w16a snapshot as soon as I saw it had been realesed for my mac osx. As soon as I got on i loaded up a superflat world and grabbed a spawn horse egg. And it would not let me place it, instead it just made me keep breaking blocks (it does the same when i try to place regular bocks too) and I use the default controls.
Related issues
Comments

This isn't just on creative, it is on survival and on servers too.
Duplicate of MC-13841.