This post makes me think you don't have the lens properly snapped into place..... If you don't snap the lens on properly or get it clicked and squished into all of the rubber seals, it will do exactly what you're describing.
"When I do good, I feel good; when I do bad, I feel bad. Thatís my religion." - Abraham Lincoln
Moral of the story: If your going to rob people, wear a diaper.