So, almost directly after I experienced my problem with Ubuntu and switched to Arch Linux, someone else came to me with the exact same problem that caused me to jump distros.
What is this problem, you ask? Well, if you are using GDM, the screen will blink several times, GDM will crash, and the system will eventually freeze.If you are using KDM, anyone who logs in will be immediately logged back out.
The solution came when I realized that the X server errors were, in fact, being logged. They were getting dumped as a dot-file in the user’s home directory. It was something like “.xsession-errors”. Anyway, there were two lines in the file, and one of them complained about lnusertemp.
‘Twas then that I realized I’d seen a similar error while installing Arch Linux. A kernel update or something had set the wrong permissions on /tmp. I had forgotten about it though, because the knowledgeable community had documented the error on the forums, and I found the solution quickly.
So, if you are having a problem similar to what I described, today is your lucky day! Simply start in recovery mode from grub and issue the following handy command.
chmod -R 1777 /tmp
As for me? I’m staying with Arch Linux. Ubuntu is nice, but I really appreciate the more technical-oriented community attached to Arch. The signal to noise ratio is oh-so-much higher. Interestingly enough, the reason I was using Ubuntu was because I liked having a system I didn’t need to care about breaking. I now like Arch because it’s much easier to fix when something inevitably does break.