Mine cart undestroyable/ cant exit

Normally, when you hop in a minecart, you can travel to your location needed, then exit by either clicking a nearby block or destroying the mine cart.

Now, in the new 1.6.2 version, you cannot either destroy or get out of a mine cart, making it impossible to leave it without loading a older vertion

Steps to Reproduce:
1. place a mine cart on your rails
2. get in
3. you can destroy everything around you without being able to exit