Haunted house

If ever to believe in ghosts, now is the time...tonight, I was hanging pictures (well, trying to), and the nail I had successfully sunk into the wall in the third spot I'd tried (I was having WAY more trouble than usual!), popped out of the wall as soon as I started to put the next nail in! So after 4 holes in the wall, and 15 minutes of measuring and leveling, I still don't have my pictures up on the wall, and now I have to mud, sand, and repaint two spots on the wall! Then I tried to hang a clock in the bathroom, and the same thing happened! I'm fairly certain I've figured it out, but for awhile, I was concerned about what might be living inside my walls! So much for being productive tonight!