Version: (using KDE KDE 3.5.5) Well, change layout and KMail changes order rule and sorts again all mail.
I think I reproduced this once, but couldn't on subsequent tries. Can you give the exact steps you take to get this problem?
Gosh, it is crazy -- before I posted this report I fiddled with message structure viewer. Changes reordered mail each time. But now I cannot do this again (I will try though). Would it possible this bug is active one-try only? :-)
Closing until someone can find a way to reproduce this