Minecard sound err at 1.4.2.

I rid minecart at downhill rail. I noticed that minecart's sound is not heard. So I pressed ESC key and click "Back to Game" button. And It heard minecart sound.... but that sound is heard minecart was stopped.

Summery
1. Minecart's sound is not working at 1.4.2
2. So I press ECS key(at keyboard), and I clicked "Back to Game" button.
3. Suddenly minecart's sound is working.
4. Minecart stopped, even though sound was heard a long time.
5. I did not hear the sound of the falling away on the rail, But got close again heard, Still minecart stopped in the state.