I shoot full manual 98% of the time. Recently, whenever I set up a shot (for example, f/2.8, 1/500th, ISO 320) I will press the shutter half way to focus and the camera will revert my shutter speed to 1/180th of a second and not let me shoot any faster. I do not have any sort of external flash set up - there's nothing in the hotshoe at all. I've checked all my settings and can't quite figure out why it won't let me shoot over 1/180th. I have a wedding to shoot tomorrow and I'm getting really frustrated. Any help is appreciated!!