I'm a newbie on this forum and have been following this thread with great interest. My K5 was purchased just over a week ago and has serial No 3822xxx. After carrying out the suggested f22 shot of a white sheet I find there are just a couple of marks which, at 100% crop, look virtually indentical to the two marks in the shot posted by mille 19 on 06-12-2010, one faint and the other quite pronounced. I have not attempted a sensor clean and am more inclined to return it to the dealer for cleaning. They hopefully should be able to do it better than I can.

Jim