Version: (using KDE 4.1.3) Installed from: SuSE RPMs single/double click to open: no immediate change user has to restart konqueror to make settings work. Settings: system settings -> mouse&keyboard -> mouse -> single/double click to open option.
See bug 175280 (same report for Dolphin). Maybe it's actually a duplicate because Konqueror uses Dolphin's file management code?
*** This bug has been marked as a duplicate of bug 175280 ***