Matron.
My 500D is struggling to auto-focus at the moment, which is driving me up the wall (but I'm also having fun with manual focus - a silver lining).
As I swap lenses when I'm out and about I wouldn't be surprised if something had got grubby somewhere along the line.
I'm thinking about sending off the body and the 10-20mm lens to get them serviced/checked over. Has anyone else done this, or has any experiences with doing this?