I had similar problems with a 135mm lens. I never got to the bottom of the problem, but it was only with that one lens so I suspected that it was a previous amateur repair job gone wong with the elements replaced backwards or something. I'd suggest that you beg, borrow or steal another lens to try out. That way you could at least narrow it down to either a lens problem like I had, or a camera problem.
There are a couple of focus issues that arise due to the removeable/interchangeable focus screens on the C330 series (mine is a C330f), but if my memory is correct the C220 doesn't have interchangeable screens (someone correct me if I'm wrong), so in your case I think a screen problem would be less likely.
Last edited by fenderslash; 10-09-2012 at 11:11 PM. Click to view previous post history.