Version: (using KDE KDE 3.5.6) Installed from: SuSE RPMs It happened before (-> 3.5.) it happened for 3.5.6 too :-( Not all settings are lost -- for example toolbar placement and size is preserved, but icons are added. I also noticed that option "empty trash on exit" is turned on (I keep it off) so when I quit KMail, surprise... luckily I try not to keep any important data in trash of course, but the principle of the least surprise is violated of course. I didn't notice major settings loss in KDE which happened before (good), only KMail this time.
Well, not that KDE 3.5.6 is already released, we can't undo that problem. I'll try to keep an eye on furhter upgrade paths. Closing this bug report (as INVALID, but that is just because there is no suitable status available)
Thomas, it happened on every upgrade. I had to put some version number, but you can replace it with KDE3.5.9 as well. So I hope it is rather fixed in KDE4 (i.e. when I upgrade from KDE3.5.9 to KDE4.2 the settings will be preserved).