Comment 7 for bug 805154

for me it happens also at boot..don't know why but it tries to start gdm instead of lightdm..it gives error and stops booting..then if i execute sudo lightdm it starts without problems and almost everything works (it's still alpha 2)..i found the error executing dmesg..
I upgrade ubuntu from 11.04 to 11.10 about a month ago..
for now I solved it executing in boot Ctrl + Alt + F6 and then sudo lightdm..hope this may help someone with the same problems..