Thank you for notifying me of this problem and also for providing me with the solution.
I am using tkPacman with XFCE and never had this problem.
I will start working on a corrected version of tkPacman, but I will need some time because I have not been working on tkPacman for a long time and it now seems almost like a new project to me. Also, I will have to install an Archlinux system with KDE instead of the one with XFCE that I am using daily.