My Redhat 8 machine has been running with few problems since around Christmas when I got it. With the username I made for myself I was able to use a desktop environment, console, or a barebones window manager through VNC. The weirdness started when my brother, who had a user-name since the OS was first installed but never really used it more than once or twice (except for frequent file access through SMB) decided he wanted to learn to use Linux. I had him log on to KDE and was somewhat confused when I got an error message that explained that the RHN config could not access a certain file in his home dir. Even chmodding his entire home directory to 777 didn't get rid of the error message. I saved the error, but it was deleted by mistake in the process of fixing the problem. I at first ignored the error and started setting up his DKE desktop theme and such, but none of the config options would change anything. When I clicked "apply" nothing would happen, and the desktop or window decorations would stay the same. In addition to that I could not right-click on the quicklaunch buttons in the taskbar.
Now this problem didn't go away with re-login or reboot. I would not have posted it had I fixed it by deleting his user name at that point but instead I started up Gnome instead of KDE and experienced the absolute strangest behavior:
Gnome didn't start up normally, and what I saw when I came back to the computer was a black screen with a normal menu bar at the top and an error dialog box in the center of the screen that said nothing. It was totally black except for a red "!" and an OK button. I clicked on OK and found another one right under it, about five more times. I then clicked on the file menu and found that instead of the regular options (New, Open, Rename, and such) the menu bar was a slim vertical line with no text whatsoever in it. When I tried one of the blank selections I got the featureless dialog box again. Nothing did anything, and eventually I logged in remotely and halted the system.
I logged into another user and found that everything worked fine in KDE and so I deleted the screen name and home directory (and the error message I had saved, oops) and made a new identical user with the same UID and a new empty home dir with the exact same name as the one before. It worked perfectly. I have no idea what on earth could have caused this bizarre behavior because I did very little fooling-around with his screen name. Was it something I did? Why did this happen?