http://www.dchome.net/viewthread.php?tid=974259&extra=page%3D1
(in Chinese, Babelfish English Translation Here)
This K-5 guy confirms that the problem only appears when his K-5 was put outdoor at about 10°C and his unit would back to normal when he went back indoor, which was verified.
http://www.dchome.net/viewthread.php?tid=974259&page=1#pid11467893
Whilst the user has almost been sure that his unit would not work at that a bit colder temperature, I think his unit is yet defective and it is more or less a QC/production quality problem more than a design issue.
Btw, my one-year old K-x also suffers from instability recently. Under around 10°C outdoor, it had hanged up for three times in one night during shooting. And, there were two other problems seen as well. One is the back panel LCD displayed garbage and I was forced to turn off and then on my K-x to bring things back to normal. The other thing is that it had happened for times that my K-x fires twice per shot even the frame advance mode was in Single! >:-[
Furthermore, my K-x' AF had been out after less than one-year, which I've cured almost with the Debug mode myself and most of my Pentax primes are okay in AF accuracy. But then I guess I might sell off my K-x soon as I have purchased my Custom K-r from Japan, which I think would arrive within the month.
Related:-
What Colour Scheme of the K-r Would You Choose?
How to Order a Custom Coloured K-x from Japan by Yourself?
My K-x' Time Longevity on AF Accuracy
K-x Debug Mode Tutorial - AF Adjustment