At least, there is a bug on KDE-4.5.2, that is, if the time is set back, for instance, a few hours or 1 day before, the KDE will be crashed. I had this experience last week, so that, I downgraded to KDE-4.5.1, then on the next few days (when I have passed the day that the setting made KDE crashed), I upgraded to KDE-4.5.2 again. Now, KDE-4.5.2 is running smoothly on my laptop.
A good news, if you get this problem, you don't need to do exactly what I have done. Simply, just clear the KDE cache on your home directory --please follow the guideline that has been suggested by Fabrizio Montesi on his blog-- or upgrade the KDE-4.5.2 to KDE-4.5.3 (see announcement) that has been released on Nov 3, 2010. For detail information about the bug, please refer to this KDE Bug Tracking System.