Hi All,
On my fresh install of CLD 18 (multiboot, Nvidia driver installed) I have the problem as in the title, I did nothing strange beyond setting up the DE and installing some preferred packages but the following day Plasma does'nt start.
In a nutshell, I have been doing the following attempts to log in:

ck-unlock-session -u Session1 ### etc.
su -c 'dbus-send --system --print-reply --dest="org.freedesktop.ConsoleKit" /org/freedesktop/ConsoleKit/Session1 org.freedesktop.ConsoleKit.Session.Unlock'
After that, I can log in as root but not as user (try also with new user); trying also:
emerge -e @world
got nothing.
When installing packages apparently everything gone well, the only weird point is that I have been installing
media-gfx/gmic
but it is not coming out on GIMP. Don't know if it is important, I add terminal output here:
https://pastebin.com/3kwgzPPH
Please, do someone knowing the solution for this issue?

Best Regards

Edit (15.X.2018)
I am pretty sure the problem comes from OpenGL / Nvidia driver but I don't know how to fix it

Edit (18.X.2018)
I discovered something weird today: can log in with user "guest".
I deleted the user created by me (/home included) and creating a new user, log in impossible too.
cl-update today brought kernel 4.18.14 and Nvidia Drivers 340.107

P.S.
I have been posting this question on the CLD Official Forum on October 10,2018 receiving only one answer which unfortunately does'nt solve the issue, I am posting here now hoping better luck because I should like to keep CLD on my computer.
Thank you for reading

When you say you can't "unlock" KDE, I gather you mean you can't log in. Is the computer in suspended or hibernated mode, or are you trying log in from a logged out state?

Since you can log in as root, did you look at the log files?

Also, what do you mean by "CLD 18"?

Hi Frankbell,

Thank you for your kind concern.
CLD = Calculate Linux Desktop KDE Edition, 18 is the last born.
cld-18-x86_64.iso (Gentoo Based)
I try to explain better: I switch on the computer and selecting CLD (Am in multiboot, it's a desktop machine), at beginning coming out black screen with message saying "Plasma can't start because something wrong with OpenGL etc." and after a bit another message inviting to switch to consolle and digit as root ck-unlock-session -u Session1 and another command to unlock, it does'nt work.
Searching online I found another formula/script (su -c 'dbus etc. as I wrote in my first message), I can log in as root with this one (startx).
I did some work on the distro and at present time I get the login screen but... can log in only as user "guest" or as root.
Creating new user no log in; I have been deleting the old user created by me too, still no log in creating new user.
After that can say that messages at boot saying can't find image... etc. can't find this, can't find that till getting the log in screen.
I did'nt look at the log files, I don't know which one I have to look, sddm.log? If useful for you to get clues tell me wich one between the ones into /var/log is useful for you and I get it.
Ok, I don't remember other details Ciao