Auto focus is not working properly and will not

It may be that the ribbon connector has broken in the lens.

Clean the contacts on the camera body (and the lens, too) where they meet with a cotton swab lightly dampened with rubbing alcohol.

There is a menu option to turn it on or off. Check that it is turned on here.

Check the image properties after the shoot.
Shutter speeds and Auto Focusing.

Have you choose a correct "Focusing Point" by pressing the right outmost button on the rear of the body, just above the CF card compartment door?

id recommend taking it to the canon dealers..this seems like a problem with the software

I would only suggest you might clean the metal contacts on the inside rim of the lens....just be very careful what you use....a pencil eraser is good but make sure you clean away any shavings that might get into the camera...

If you are unable to focus in broad daylight and it just hunts through the whole focus range without locking, then it sounds like a problem with sub-mirror pin (also called the second mirror pin). My 300D just had this problem and I had to send to service to get fixed. I sent to http://www.keh.com/ as they were at least $50 cheaper than going straight to Canon. Just got it backed and it works like a charm again.

I am having the same problem with my Rebel. Canon recommended cleaning the contacts on the camera and on the lens. After that they recommended sending it in for repairs. Let me know if anything works for you as mine still does not work.

Suggestion: 1. camera probably has a sharpness setting. 2. avoid wide open, F/5.6 is the sweet spot on most lenses.