I don't think it's just from version .05 because I haven't installed that one yet and I've seen that about 4 times now. Although mine were actually standing, but they "floated" or "slid" across the floor instead of walking. Really creepy looking, isn't it?

I just checked and mine is still version .04, but when I put the antispam into the computer, they both slid down those stairs going from the hall with the bedrooms/bathroom down towards the den/laundry room. So, it definitely happens with the .04 version as well.