Comment 1 for bug 1454004

I have similar issues with sddm. Randomly it stops working and I end up to the sad black screen after logging in. So far I've managed to "fix" it by copying another working users .kde and .config directories, but that does not help anymore. Logging in as the other user works.
Check this bug:
https://bugs.launchpad.net/ubuntu/+source/sddm/+bug/1431332