Strange focus prob with Canon XT

Anyone else have this happen? When my camera is in auto mode, it focuses on objects or people fine, but when in manual mode with auto focus it cannot focus on anything - i have to use manual focus, which can be a real pain if i'm trying to shoot fast or if i'm shooting a virtual tour. I never had this problem before, it's recent.

Any ideas on why it would suddenly do this?

are you using the correct focus points? Like did you try just defining the center one and focusing with that point?

Yeah, I checked the settings, nothing had changed and it was centered. I actually cleaned all the connection points on the lenses and on the camera tonight with a q-tip and alchol, wondering if maybe their was a connection problem, cleaned the senser and cleaned the mirror and lenses really well too. I found a little piece of hair stuck on the mirror inside the camera that may have been causing the issue. Whenever i tried focusing on anything, the lens just went back and forth and back and forth. It seemed a little better after getting that hair out. I'll give it a more thorough workout tomorrow to check the focusing issue.