DPP? Sorry I'm new to some of these acronyms...
Canon Digital Photo Professional (DPP), the software that comes bundled with the camera.
Not sure if it works with a Mac.
Just notice your using a T1i which unfortunately doesn't have micro adjustment. If it is front focusing the only options are to send it to Canon with the body for calibration or getting another lens. Do you have another body or lens to try and identify if the front focusing is due to the lens or the body ?