Bug "works" only with redstone-torch on side, not on top

How to reproduce:

• Reproduce the situation in picture 1.
• Set a (solid) block on top of the redstone, the torch should turn off now (Picture 2)

It also works the other way round:

• Reproduce picture 2 (except of the torch having the state it shoud have)
• delete the block on top of the redstone, you get picture 1, but with the torch turned off.

Hope my english isnt too bad to understand ^^