Trapped in an endless cycle of login

[manic_b]

Pretty much what the title says: I try to login, I get a brief black screen and then I'm back at login again.

I've just got back from a few weeks away. Did a bug update through the update manager, rebooted, then this. Tried booting in recovery mode and repairing packages (which took a while, looked like it was doing a lot). Tried installing lightdm which gave a different-looking screen with a blue-purple gradient and the same problem; uninstalling lightdm left me with the same screen (must be a kde default or something? No idea how to actually activiate lightdm in that case) and the same problem. Reinstalled kdm a few times, no luck. Reinstalled xinit, no difference. Rebuilt my nvidia drivers, they seem happy (and the splash screens look fine in any case).

ctrl-alt-f1 to a terminal, which *does* let me login:
"startkde" gives:

Code: Select all

$DISPLAY is not set or cannot connect to the X server

"startx" gives:

Code: Select all

Fatal server error:
Server is already active for display 0
    If this server is no longer running, remove /tmp/.X0-lock and start again.

Please consult the X.Org Foundation support
    at http://wiki.x.org
for help.

ddxSigGiveUp: Closing log
invalid MIT-MAGIC-COOKIE-1 keyInvalid MIT-MAGIC-COOKIE-1 keyxinit: giving up
xinit: unable to connect to x server: Resource temporarily unavailable
xinit: server error

[manic_b]

(Oh, and df suggests that I have plenty of space in my root partition, which is the usual suspect for this problem.)

[manic_b]

Unfortunately, nothing has changed

[manic_b]

As suggested elsewhere I tried creating a new user and logging in; this didn't work. Suggests that it's not something in my /home directory, I guess.

[manic_b]

Yup. From lsb_release -a:
"Description: KXStudio 12.04.1"

Kernel just updated to 3.2.0-51-generic

Purged lightdm, reinstalled kdm a couple of times; I'm still getting the purple background, but ps -A confirms that kdm is running.

And I can now log in. WHAT. Well, this is good, but I wish I could leave more helpful advice for the next guy than "reinstall lots of things repeatedly and rage a bit."

Still: thanks falktx, you're the best