I'm having the same issue. Mine started after installing AMD proprietary drivers, having them fail to work, then uninstalling. This was all done following the linked instructions on AMD's website. First reboot after the uninstall, and I can't login as me. (Additionally, my username had changed to the Full Name specified on the account). I could still logon as Guest. I changed the Username on my account back to what it used to be, but still cannot login.
I can login, using my correct Username and password, from TTY1. Even so, I did sudo passwd *insert username here* and was able to set my password, even though I was setting it a password that already works.
Also, as my account is Administrator, every time I sudo I have to use my password, and it has continued to work.
Doing the above I get
Originally Posted by steeldriver
-rw------- 1 username username 1908 Mar 5 17:12 /home/username/.ICEauthority
-rw------- 1 root root 251 Mar 5 16:43 /home/username/.Xauthority
Anyone have any idea how I should proceed?