Villagers Disappearing

So, me and my friend have a server running Minecraft release candidate 1. Only we can join.  i went to trade and the villagers had simply disappeared. Its all closed in and protected so a zombie wont have killed them. They had really good trades. This happened again once we got some more. There is no log files about this issue. Then we made a new Minecraft word to test it out. and sure enough, they'd disappeared. This also happens in local worlds.