http://forum.xitek.com/showthread.php?threadid=918700
(in Chinese, Google English Translation Here)
As it can be clearly seen, oil is leaked inside the lens and thus caused fogging. That's it:-
The Pentax user also mentioned that he opted to send in his K-r together with the DA70, of which the repair is mandatory, for "calibrating" his body for the yellow-light front focusing. But it is just worthless at the end of the day, because every K-r is just the same regarding this!
Read Also:-
Dirty Pentax Lens Factory, Dirty Glass! :-(