I host a server and play almost exclusively SMP as a result, and it seems like this is a bug related to the Unbreaking enchantment. From what I can tell, the client and server are having a disconnect somewhere, causing the client to say that the item "Broke" and remove it from your inventory temporarily, until the server corrects it and gives you the item back.
Kenneth Willcocks
I host a server and play almost exclusively SMP as a result, and it seems like this is a bug related to the Unbreaking enchantment. From what I can tell, the client and server are having a disconnect somewhere, causing the client to say that the item "Broke" and remove it from your inventory temporarily, until the server corrects it and gives you the item back.