Every time I try to start KMail, I get an error message stating that "only one instance of KMail can be run at any time." The error dialog box states that it is already running under a PID number. How is this possible if I am not running any KOffice applications at all? Or is it running in the background? Help!
some times I have a same problem and I found out that you can fix it by removing the lock file in .kde/share/apps/kmail directory. There might be same kind of lock file for kontact also(I don't have kontact running now so I can't verify that).