First off I know there is another thread on this topic, but it seems to have died without the big question being answered so I devided to make a new thred...
It is recently been brought up that the K5 may be more prone to, or amplify the effect of purple fringing in high contrast situations. For those that owned a K10, it was known to be particularly more sensitive to PF/CF than lets say the K20 or the K7, and now it sounds like the K5 may have the same quirk.
Here is a review that specifically discusses the issue.
Field Review: The Pentax K-5 (Day 3) The Phoblographer
It would be great if someone could setup a scene with high contrast (in front of a window, or bright lamp) and take some comparison shots with the K5 and K7.
If you are curious, the other thread is called "CA/CF evaluation..."