So, KDE 4.10 just came out last week, the Arch repos sometime thereafter, and I updated today. I really love new versions of KDE–honestly–but this time something really bizarre happened. I updated, rebooted to the new kernel (I was running 3.7.4, the update was to 3.7.6), fired up KDE, and started loading my usual applications.

Then nothing worked quite right. I’d open one window, and the others I had open would disappear. Opening the launcher would also exhibit this problem: Open terminal windows would disappear the instant the launcher was clicked or any other application (including Dolphin) was opened. Infuriating. It seemed that I couldn’t have all my usual windows open at once–everything would disappear!

Fortunately, after some trial and error, I found the culprit. This latest version of KDE has made significant changes to ~/.kde4/share/config/kconf_updaterc. So, there’s two solutions:

Easy Mode

Log out, switch to a virtual terminal (ctrl+alt+F1), log in from there, and delete the file ~/.kde4/share/config/kconf_updaterc. Then switch back to X (usually ctrl+alt+F7 or F8) and log back in to KDE so it regenerates the file. Enjoy!

Hard Mode

Follow the previous steps but retain a backup of your .kde4 directory. Then run a diff on the two versions of kconf_updaterc and figure out what you want to keep, what line caused the problem, and retain as many of your previous settings as possible.

Otherwise, I hope this saves you some difficulty if you run into the same thing I have!

February 13th edit:

It seems that this post by “George” on the Arch Linux forums indicates a potentially easier solution, which is to change the window transparency settings. I changed the title transparency settings, but I’m not entirely sure if this will resolve the disappearing windows.