Can confirm this occurring in 1.4.2
The above comment (Jon's) seems typical when in gamemode 0 (I get the same if not similar results). It does seem a little more stable directional wise when in gamemode 1 (creative), however i did notice that i was brought out at an odd facing sometimes, unfortunately it seemed random thus unrepeatable.
I can confirm this still occurring in 1.4.2
The effect is purely visual where it appears the damage remains but when another zombie tries to break it, the cracks disappear and begin again.
I too have noticed this bug after 1.4.1 came out, and still persists in the 1.4.2pre released on the 24th october.
I discovered it in a different manner also, affecting boat floating mechanics somewhat because the boat elevator that i had was acting up. i've taken a few screenshots of a miniature experiment i did on the bug... Put simply, when a boat is placed on the iron block (first pic), a Ghost image of the boat sinks through the blocks and out of site, however the boat itself remains, you can tell, because when you move towards the iron block, the boats image reappears and the boat moves away.
Start
Placed
Sinks
Disappeared
Move closer
Reappears and moves away
The behavior i was expecting was that the boat would rise due to the water, or remain stationary on the block if a change has been made to prevent the floating behaviour.
Perhaps some sort of desync, looks like the sort of thing u would see in a multiplayer server where the server isn't agreeing with the client.
I'm running Java version 1.7.1_07 64bit, have windows 7 64bit
can confirm bug. MCv1.4.2
Do not need to get into cart to produce the sound. Bug also occurs with "Minecart with Chest" and Minecart with Furnace".
Some interesting behaviour I noticed, if the cart starts moving without the player in it, the sound effect is quieter (intentionally i'd assume). However, if you alt-tab out of the game and then back to the game by pressing "back to game" the sound does not disappear, it infact gets louder as if you were in the cart.
Windows 7 64bit, Java 64bit v1.7.0_07