nearly every other boot I get "Low Graphics Mode" message.

[ 8.459] (EE) RADEON(0): [drm] failed to set drm interface version.
[ 8.459] (EE) RADEON(0): Kernel modesetting setup failed
[ 8.459] (II) UnloadModule: "radeon"
[ 8.459] (EE) Screen(s) found, but none have a usable configuration.
[ 8.459]
Fatal server error:
[ 8.459] no screens found

Text of the error message:
The system is running in low-graphics mode
Your screen, graphics card, and input device settings could not be detected correctly. You will need to configure these yourself.

Usually before I get the error window, it switches to a text screen where log information is displayed. Near the end of the log are a bunch of [stopping] (or something to that effect) messages these come after a bunch of [starting] messages Both types have an indication of success on the right end of the line. there are no indications of failure.

At least twice after rebooting, when I log in, I get a message about xorg crashing (which I allowed it to report).
The notify has been crashing with some regularity as well.

I have stripped out the timestamps so I could do a diff of the two log files (there is probably a way to skip the first n charactors of each line in diff, but I did not see it in a quick look at the docs).

Attached is a diff of Xorg.0.log files between a good boot, and a boot where the graphics dropped into low graphics mode.

The first thing in the log that shows an error is the "setversion 1.4 failed". Things go south from there.

What is "setversion"? What is it trying to do? Why would it fail?

different boot failure today, never made it to the "low graphics mode" screen. It stopped with the following text on the screen:

process 422: arguments to dbus_server_disconnect() were incorrect, assertion "old_refcount > 0" failed in file ../../dbus/dbus-server.c line 786.
This is normally a bug in some application using the D-Bus library.
process 422: arguments to dbus_server_unref() were incorrect, assertion "old_refcount > 0" failed in file ../../dbus/dbus-server.c line 749.
This is normally a bug in some application using the D-Bus library.

I found this in the boot.log

Nice of D-Bus library to blame something else, but not bother to name that something else.

Another symtem to add: I have been getting long seequences where it boots only into low graphics mode. (5 or 6 boots in a row). I have not had the patience to see if it would eventually recover on its own, but booting with my second monitor (HDMI) disconnected seems to exit the sequence. Once booted, I can re-connect the HDMI monitor and the system will automatically detect & enable the second monitor.

I'm not so sure that this is a duplicate of that bug. I did not have the proprietary drivers installed when I upgraded. This bug should have nothing to do with the proprietary drivers.

I think this is a race condition durring boot. The last two boots were sucessfull I think because I was continuously moving the mouse. The last 20 or so boots failed unless I disconnected the HDMI cable.

I have removed the duplicate link since this bug has nothing to do with the ATI proprietary driver that I am NOT using.

There was an update to the kernel about a week ago. This reduced the likelyhood of the failure, but did not eliminate it.

Status changed to 'Confirmed' because the bug affects multiple users.

Same issue with a Intel sandy bridge system. But the problem started to show up around a week ago, probably after some update. before that 12.10 worked fine. The trick suggested here https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/995397 (restarting lightdm) will get it running again.
The Xorg log (complete log attached):
Fatal server error:
[ 1.840] Cannot run in framebuffer mode. Please specify busIDs for all framebuffer devices
[ 1.840]
[ 1.840] (EE)
Please consult the The X.Org Foundation support
  at http://wiki.x.org
 for help.
[ 1.840] (EE) Please also check the log file at "/var/log/Xorg.0.log" for additional information.
[ 1.840] (EE)
[ 1.843] Server terminated with error (1). Closing log file.

Replaced lightdm with gdm and have now restarted the computer about 10 times without any "low graphic mode" problem. It seems to be a lightdm issue more than a X.org one.

I am having the same issue with a system with dual vga nvidia optimus and intel (I don't use nvidia proprietary drivers or any thing). I would be happy if intel starts always correctly.

I tryed to compare log files of xorg and they start differentiating with line "setversion 1.4 failed"
In the good log file (the one that system starts normally) the order of loading moduls is:
[ 6.071] (==) Matched intel as autoconfigured driver 0
[ 6.071] (==) Matched nvidia as autoconfigured driver 1
[ 6.071] (==) Matched nouveau as autoconfigured driver 2
[ 6.071] (==) Matched nv as autoconfigured driver 3
[ 6.071] (==) Matched intel as autoconfigured driver 4
[ 6.071] (==) Matched vesa as autoconfigured driver 5
[ 6.071] (==) Matched modesetting as autoconfigured driver 6
[ 6.071] (==) Matched fbdev as autoconfigured driver 7
[ 6.071] (==) Assigned the driver to the xf86ConfigLayout

in the other one the secuence is:
[ 7.362] (==) Matched nvidia as autoconfigured driver 0
[ 7.362] (==) Matched nouveau as autoconfigured driver 1
[ 7.362] (==) Matched nv as autoconfigured driver 2
[ 7.362] (==) Matched intel as autoconfigured driver 3
[ 7.362] (==) Matched vesa as autoconfigured driver 4
[ 7.362] (==) Matched modesetting as autoconfigured driver 5
[ 7.362] (==) Matched fbdev as autoconfigured driver 6
[ 7.362] (==) Assigned the driver to the xf86ConfigLayout

as you can see, it seems like the drivers are recing which one has to start first and if intel starts first it works other wise fails.

 if you need both full log files or any thing I can do to help please let me know.

another problem I have (not sure if related) is that when starting with a second monitor connected the system hangs with a black screen.
this happens after selecting to boot on ubuntu (I have dual boot sytem).

64-bit 3.8.0-9-generic #18-Ubuntu SMP Thu Feb 28 17:02:06 UTC 2013
Desktop with Intel e8500 cpu, Nvidia GT9500 and default (non-Nvidia) video driver.

I get this problem frequently following a restart from 12.04.

Pressing the reset button or executing a FULL power shutdown prior to completion of booting 13.04 will usually eliminate this problem. This would imply that a hardware state that is properly initialized following a reset or full power shutdown is NOT being properly initialized during a warm reboot.

On occasion, I have also had to update/install grub, either from 12.04 or a via fix a broken system from a server CD.