Put the summary of the bug you're having here

What I expected to happen was...:
when you click on anything in the inventory it is supposed to instantly be "picked up" by the cursor and so double clicking should pick up the item and place it back.

What actually happened was...:

there is a slight delay when you click on any item and this causes things like double clicking to pick up and then it does not go back but remains in your cursor until it is again placed back.

Steps to Reproduce:
1. open minecraft 1.4.7 or below
2. open minecraft 12w04a
3. pick up something in both games and double click on it ( item must be placed in inventory and not on the cursor before double clicking)