Hey there, sorry for the lame question, but I'm new to this and hoping I can get some help! I just got my hands on a Canon Rebel XTi, and with it came a Sigma Zoom 28-70mm F/2.8-4 lens, and it just has problems focusing. With AF, it would just click and on manual, no matter what I try the lens can't focus on anything, near or far. Is this just lame user error or do I have something I need to worry about? And as for the body, I'm pretty sure the problem isn't in the body itself because I was able to use a 300mm lens just fine. Thanks!