Put the summary of the bug you're having here

I wanted to make with /entitydata @e[type=Item,r=5]

an item Invulnerable.

but the item gets invisible and in the item falls 1 block in the ground!

1. make one Item Invulnerable with /entitydata @e[type=Item,r=5]

2. make fire or lava in the item

3. now the item gets invisible and in the Block under it!