I have Canon EOS 450D, and it seems, that camera have problem with autofocusing, when i'm looking through optical viewfinder. If I switch camera to liveview - autofocus works correctly, but slow. The problem popped, when i bought canon 50mm F1.8 II lens - it focuses terribly, even on inf. - looks like it's front-focused. Sometime ago i've heared, that there's adjustment screw, behind the mirror, and it's possible to adjust it, but i'm not sure - will it help, or i'll broke something.
And yes, there are no service centers near me, so i can't give camera to professionals.
Any advices? May be there's a way to adjust autofocus via some software?