Comment 33 for bug 871667

It appears that lightdm 1.2.3 still has the problem.

The issue cropped up in an install of 64-bit Mythbuntu 12.04, after it had been running fine for about 15 months.
The nvidia 6150 chip was failing and locking up the system randomly, so it was replaced with an nvidia 8600GTS PCI-E card.
After the first successful boot with the 8600GTS card, the user could not log in to the PC, until the /home/username/.Xauthority file ownership was changed from root to the users username.

The /var/log/lightdm file shows that lightdm 1.2.3 is running.

[+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.00s] DEBUG: Starting Light Display Manager 1.2.3, UID=0 PID=1351
[+0.00s] DEBUG: Loaded configuration from /etc/lightdm/lightdm.conf
[+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager

The following files are in the apt archives on the machine, dated July 19, 2003:
/var/cache/apt/archives/liblightdm-gobject-1-0_1.2.3-0ubuntu2.3_amd64.deb
/var/cache/apt/archives/lightdm_1.2.3-0ubuntu2.3_amd64.deb