See what this K-5 user found and reports (with sample photos):-
http://forums.dpreview.com/forums/readflat.asp?forum=1036&thread=37503804
It seems that the material of the AA (Anti-Aliasing) filter of the K-5 is being changed in status by the heat generated by the LiveView, so that the UFOs/pearls are accumulated and appear (on sensors and images produced) eventually. In fact, this has been suspected by some other affected K-5 users before, that is, their brand new units did not have the UFOs/pearls appeared but which were yet seen after a certain period of time with more use.
One of the reasons I decided to go (a Limited) K-r instead of a K-5 is yet because of this IMHO major unresolved issue with big uncertainty. Indeed, there is NO direct *official* statement of any from Pentax/Hoya for what has/have been wrong and what's going on about all those happenings.. >:-[
Previous Related:-
http://ricehigh.blogspot.com/search?q=K-5+Sensor+Stains
And Read Also:-
Ten Reasons for Thinking Twice before Decided on a K-5..