Vidmantas

check server twice. that was in my case 🙂 you can freely play it with 1.5.1 client on 1.5 server and only on 1.5.1 server

It does not work in 1.5.1 for me. even with simple furnace with hopper under it. placing lava bucket or empty bucket leaves it in place.

Edit: tried setting "force update" on the client and the results are the same
Edit2: in duplicate thread found about server not beeing 1.5.1... well this works perfect in single player.