Version: 1.2.4.2a

I enchanted a ring with "Step Up" 1 and equipped it. The enchant works fine in the wild but now I can't enter my house anymore. Here's a screenshot:
http://i.imgur.com/Ipf3glS.png
As you can see, there are lower half slabs that then go up to a full block with the door and that's where "Step Up" doesn't work. It looks like it needs an additional half block and if I break the slab above the door or put it in the upper half of the block above the door, it works again. But with the way it is at the moment, I have to use my jetpack and fly up the half block.

Edit:
http://i.imgur.com/5Uz25c7.png
Going through the 1x2 hole on the left does work, even though it's basically the same thing, apart from the block in the roof in front of the hole/doorway.