It looks like there is some Chromatic aberration present - When the colours focus at different points on the sensor.
What lens are you using? Is it a Canon lens? Has it had a knock? Have you tried using another lens?
or, Maybe the sensor is loose and not holding in the right plane - That has been a problem with some Canon EOS digital cameras.
Are you using full auto? If so try it on aperture priority and close the aperture a little with slower shutter.