I can confirm that. Forge fixes the problem. Vanilla can't run more than 8 zombies without hitting 100% CPU usage. With Forge I could spawn tens of zombies and not go more than 10-20% over the normal usage. Sad that modders have to fix what Minecraft devs did not.
Confirmed in 1.4.6 SMP, 3 dogs, owned by 2 players, disappeared at the same time.
A diamond pickaxe with Efficiency V desyncs gravel/dirt/sand, blocks disappear clientside, but the server won't let me go past the space they've occupied. Refreshing the blocks reverts them back into existence.
Minecraft 1.4.6
Oracle Java 1.7.0_10
It started happening after 1.4.4 update. A torch flame flickers around the scene. It's so fast I didn't even bother making a screenshot. Those videos pretty much show what's going on. Thanks for posting them.
I have the same issue. Placing blocks and opening or closing doors or gates is often repeated due to visible lag (not a mouse issue). The lag happens exactly at the moment I place a block or open/close the door, so there's no avoiding it. There's a portal chamber and a multilevel basement beneath the area the lag occurs. I've seen someone mentioning on reddit, that due to a bug, every time you update or place a block above an empty chamber (room, ravine, cave etc.), the game updates the lighting in that chamber, and this creates lag. I don't know if that's the case, unless someone else says so, I'll stay at "No".
I play on a LAN SMP server (Minecraft v1.4.2, Oracle Java 1.7.0_9, Ubuntu 12.04, 2GB RAM, 1.5GHz Dualcore Atom) set up on a separate machine, with 2 clients connected, both having the same issue in the same area.
Confirmed. I rolled my server back to 1.7.10 from backup, and recreated all the portals (as suggested in a comment above), then updated it back to 1.8. That seemed to fix the issue as every portal was linked properly after the update.