I never thought its possible but you wouldn't believe how a little baking soda saved my Cannon Powershot A560 camera.
My camera suffered from a bad case of corrosion on the batteries electric contacts (dont leave batteries inside for too long... ). This caused the camera to always shut down and show the "change battery" sign (even if i just changed them).
1. Baking Soda and water
2. Tooth brush
5. small screwdriver
This was performed on a cannon camera but can be implemented on any other brand.
WARNING - use this instructable at your own risk. if you do something wrong your camera might not work anymore. if you have waranty - use it!
This is a last case scenario (dont want to pay for repair and dont care if you break it)
All you need to do is:
1. Expose the contacts using the screwdriver (in my model i had to open the entire camera).
2. Soak the toothbrush in the water with the baking soda.
3. Scrub the contacts hard (make sure to get rid of the greenish layer) Warning! be carefull not to get any electrical component wet.
4. Use the toothpick and the sand paper to sand the remaining contacts (expose the metal - it should shine when you finish this step)
5. Reassemble the camera.
6. Your done! it should work fine now.