The evidence I have personally seen suggests haunted houses are, in fact, real, without given any particular credence to any particular explanation of what the haunting is. In particular, I own a house in which bizarre crap has happened since I first moved into it. Persistently. I've moved into another house, and have been making repairs in preparation to sell it; most recently, in a room with almost no furniture, in a space with absolutely no furniture, a key was dropped by myself. Four people searched the area for significant periods of time on three different occasions with no luck. I found it on the floor a week or two ago on top of something that wasn't there when it fell. Which is the straw that broke the camel's back in terms of my skepticism.

Other bizarre things that have happened include such things as my waking up to discover my recently-purchased bottle of key lime juice had been placed in the oven, and the oven turned on; the plastic bottle had just started to melt when I made the discovery. Another situation involved my sister, who one morning (while home alone) walked into the living room and discovered on a previously empty floor three sonograms of the previous occupant's baby. (There were -many- other things; I'm choosing for the purposes of this post the most unusual and least prone-to-outside-explanation occurrences. Night terrors, for example, are easily explained.)

Well that ... sure is weird. Are you planning to set up hidden cameras? Cameras seem like they should deal with most of the competing hypotheses here.

I must say, this seems like it should take a human. Whether hiding in the walls or sleepwalking & high on mold. Even if you couldn't rule out ghosts, they don't seem to fit.