Can not pick up some of witches drops

I can confirm this - I let the witches drop aprox. 30 blocks, and some of the dropped entities are ghost entities.

The entities can be moved by water streams as well as item elevators, but are still untouchable when they lay still. If another entity of the same kind is dropped on top of the untouchable entity, they stack together allowing the dropped entity to be picked up and the untouchable entity to be removed.

Replicated in SMP (1.4.5 jar)

// O

Duplicate of MC-4.

I don't think this is related to MC-4, but rather that it's a problem that only affect drops by Witches specifically.
On the server I play on, which is currently running 1.4.7, I can reproduce the bug in my Witch farm as well.
The method of killing the Witches doesn't matter, and what makes me think it's not related to MC-4 is the following:
Let's say a Witch drops, for example, 1 Stick, 1 Gunpowder and 1 Glowstone Dust. Sometimes, I can pick up only the Gunpowder and the Stick, but the Glowstone Dust turns out to be a ghost-item that I cannot pick up, eventhought it landed in the EXACT same spot as the Stick or the Gunpowder.
The Witch drops don't have to land on the edge of a block for this to happen. Therefore I think this is unrelated to MC-4.

edit: I can also fully duplicate what Olle Görling said.

This ticket is not a duplicate of MC-4.

I can also confirm this bug is present in 1.4.7.

Most of the time, only some of the drops from witch are able to be picked up. This isn't an issue between the client/server disagreeing where the item is, as it affects other players on the server the exact way, no one can pick up the items.

drops cannot be picked up

If witches die on hoppers, ALL drops go into hoppers.

That is true, but the ghost items visually go into the hopper without actually appearing in its inventory.
Can someone please open a new ticket for this bug? It's not related to MC-4 for sure, I just don't have enough information on what's causing this bug.