I confirm this bug.
If i trade with "shift"-click, i buy goods for all the emeralds that i gave to villager. And after trading my emeralds fall from me to ground and at my inventory i have only a small part of purchased goods.
All mobs sink into ground.
This bug begins from Minecraft 1.3 update.
Confirmed in 1.4.5.
Very annoying bug!
It seems that Mojang don't test their updates before release? Maybe yes.