Reset the camera settings using the instructions below:
1. In Picture-Taking Mode, press the Menu Button.
2. Press down to highlight Reset all camera settings
3. Highlight yes, then press OK.
4. To return to Picture-Taking Mode, press the Shutter Button halfway down.
Next, the one thing that even experienced photographers miss is that a single small spot or smudge on the lens can cause the problem that you are having. Carefully clean the lens and look for any scratches. Depending on the environment that you are shooting in, a haze can build up on the lens and cause incorrect readings and the shutter may not release until accurate focus has been achieved or the camera will focus at the wrong distance.
Please keep in mind that my diagnosis & solutions provided are directly dependent on the accuracy of your description of the problem. As with any "do it yourself" fixes, success is a "team effort", since I can't see or touch the camera, and relies on the customer's manual dexterity and ability to follow the instructions well.
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