It works when using e.g. Shift+F11 or anything else. When you try to switch back to default (Shift+F12) switching header/implementation fails. KDevelop 3.3.2-0ubuntu3 on Kubuntu Dapper Drake (latest upgrades from Mon 8 May 14:40:43 CEST 2006). -- Shift+F12 does not work https://launchpad.net/bugs/40252