Focusing Problems with my Canon Rebel XSI

I have had this camera for about a year now and it worked great for several months. However, the last 4 months with this camera has been a nightmare because I can no longer focus consistently. When I first purchased the camera I am almost positive I could focus on an object at any distance. Obviously if an object was far away I could only zoom to a certain point, but the camera would zoom as close as it could and take the picture. Now if I try to zoom in on an object at a distance the camera will not focus enough to take the picture in auto mode. I can manually take the picture, but the picture is fuzzy. For instance, if I am across a room and try to zoom in on my son on the other side the camera will not focus and take the picture.

 

Have you contacted Canon? If it's still under warranty they have an obligation to repair it.