Originally posted by Robin CB
Thanks Brian. I will have a play with the menu as well.
EDIT:
I have just checked my menu - AF Mode is greyed out and AF.S is alongside, but I don't seem to be able to change it.
My firmware is up to date (or as up to date as a K100D can be), so it looks like I luck out there.
What shooting mode are you on? Some of the modes will force the AF behavior, 'Sport' mode will force AF.C, 'Macro' and 'landscape' will force AF.S and probably others. Try putting it in "P" mode or any of the M, Av, Tv.
I've never cleaned the AF sensor on mine either, but it's pointed to in the photo here:
K100DS_AF_Module.jpg Photo by RiceHigh | Photobucket.