Fantastic, except for the recent CATASTROPHE

I have owned the Canon PowerShot SD600 for 8 months and have always been happy with the quality of the photos and movies (after reading and understanding the Basic and Advanced instructions, of course). But in one, inexplicable split-second, I can't understand why the camera's functions ceased operating. I can no longer access any of the features of my Canon PowerShot SD600. When the camera is turned on, to either the photo or movie functions, it zooms to the tightest setting. The zoom does not work, neither do any of the other function buttons. The only buttons that work are the on/off and shutter button (sometimes, but not in movie mode).