Even I found the same problem creeping in when I did a custom installation of Red Hat Linux 8.0. When I logged in as a normal user say, mickey through KDE, I got the error which you has highlighted.
What I found is, there are some files created under /tmp. If /tmp does not have permission, it does not show any errors as you have mentioned, but it never lets you log in. It takes you back to Login screen. Coming to the error which you faced, there is a directory by name, ".ICE-unix" which gets created. So when a user tries to login for the first time, some files are created under this /tmp/.ICE-unix. So if this ".ICE-unix" directory does not have write permission for normal users, it gives you those errors which you have highlighted.
I gave full permission to /tmp/.ICE-unix directory, and I was able to login to my new user created. Hope this helps, atleast to someone who is trying to solve the same error.
