I've updated my repositories on synabtics the upgraded firefox to newer version, when I open it it crashes, while this I was having my hard drive plugged .. so I tried to reboot to fix Firefox crash .. From that point I can't login, tried many solutions as I can. Additional information could help you solving my problem that my computer reading the unplugged hard drive with its two partions .. tried to unmount it but with no success.
Almost same as Ubuntu login loop
enter comand line
login as root and
to see files then delete .Xauthority .Xauthority-c .Xauthority-l .xsession-errors .xsession-errors.old files
rm -r .Xauthority .Xauthority-c .Xauthority-l .xsession-errors .xsession-errors.old