Version: (using KDE 4.2.2) OS: Linux Installed from: SuSE RPMs when you have kde4 set to "restore last session on login", and do NOT quit kontact before you logout, you have a fair chance that it gets the same PID as last time, getting you a false "kontact is already running" popup.
I can confirm this bug on Kubuntu 10.10 and 11.04. It happens 100% of the time when restoring the last session on login.
*** This bug has been marked as a duplicate of bug 185544 ***