Is that the user should open the SD card door instead of closing it! Otherwise, it won't work:
http://www.dchome.net/viewthread.php?tid=986059&extra=page%3D1
(Traditional Chinese, machine-translated English page here)
So, someone may point out and would ask (as already in the above thread), the K-7/5 have the focus correction function built-in already, from -10 to +10, why bother then? The reason as answered by two different K-7 users in the above thread is that, "It is just not enough, the error is just more than that and beyond!" :-o :-(
As for my new K-r, I now face the same situation. The lucky thing is that my K-r's AF is reasonably accurate under sunlight and white light source, but when under tungsten, even a -10 correction factor is not enough but yet I don't know how to enter the Debug mode for the K-r! Really too bad!! >:-{
Btw and in fact, my K-x suffers less from the "Yellow Light Symptom" than the K-r. I shall show you folks why and how with a simple experiment together with some illustrations later on when I have the time! Stay tuned!
Related:-
http://www.google.com/search?q=Debug+Mode&btnG=Find&domains=ricehigh.blogspot.com&sitesearch=ricehigh.blogspot.com
AF Accuracy's Dependency on Lenses and Yellow Light
K-5 Low Light Front Focusing Issue - The SAFOX *Plus* System Simply Does NOT Work at all!
Is the AF Accuracy of Pentax K-5/K-r Really So Bad?