I have updated to the latest version this morning (5 June 2013).

Put the summary of the bug you're having here:
When I put an item into the furnace (top) and then go to put coal in the bottom, it will not be placed into the furnace. Also I can not retrieve the items again without breaking the furnace to pieces (with pick axe).

What I expected to happen was...:
The item would be placed into the top and bottom of furnace and be smelted.

What actually happened was...:
Nothing. The items got stuck.

Steps to Reproduce:
When I put an item into the furnace (top) and then go to put coal in the bottom, it will not be placed into the furnace. Also I can not retrieve the items again without breaking the furnace to pieces (with pick axe).