For the past couple of days (since I've updated the firmware to 1.13) I've been having inconsistent exposures. Every couple of shots will be very underexposed, and the difference is in shutter speed (not aperture, which is overexposed when it gets the dreaded sticky situation). Whereas the normal exposure might be 1/250 second, the camera will shoot an odd frame at 1/850 or 1/900 and underexpose by several stops. I'm using auto ISO. Anyone else heard of this problem or experienced this phenomenon?