I upgraded to 12.04 Tuesday (1 May) and as of 3 May the GUI has hung 4-5 times:

1. the clock stops moving


2. the mouse cursor is responsive, but nothing happens when I click


3. I can ssh to the machine

I have tried killing various processes, but have not found which to kill to make any difference, so I end up rebooting.

I applied an update from yesterday (which was a new kernel) and that has not helped.

Linux berlioz 3.2.0-24-generic #38-Ubuntu SMP Tue May 1 16:18:50 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

Machine: Intel 2 Duo X6800, Asus P5B Deluxe, Graphics: NVidia GeForce 7300GS (256MB)

I'm not using Unity (gnome3 instead), I did not install compiz, but I don't know if it's installed.

Obviously this makes it pretty much unusable. What can I do to capture some information so that someone can tell what's going on and I can get a fix? Or is there any process I can kill that will allow me to avoid a reboot? If this cannot be fixed soon, is there a way to move back to the previous working release?

EDIT:

I followed the suggestions in the answer to this question: https://askubuntu.com/questions/130387/stuck-at-login-screen

And now my system will not boot. The last line it gives is:

• Starting TiMidity++ ALSA midi emulation [OK]

(this happens consistently upon a full boot -- I suppose I need to see what's happening next in the boot, or perhaps remove the TiMidity thing in recovery mode somehow)

EDIT2:

I was able to boot in recovery mode after changing the gdm to use lightdm, I can not boot normally. I will try to see what's happening in dmesg if the hang happens again.

EDIT3:

dmesg output at the time of the hang:

http://pastebin.com/JNVDHcyg

EDIT4:

I have filed this bug report:

https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/994306

EDIT5:

Another data point, this seems to be related to the multiload indicator that shows multiple bar-graphs in the Gnome panel. I switched to this type of system indicator when upgrading to 12.04 (I previously used a different one that showed only a single bar graph, but I could not find that one again after I updated)

Here is a link to the multiload-indicator that seems to be causing the problems:

http://www.omgubuntu.co.uk/2012/02/easily-monitor-system-resources-in-ubuntu-with-indicator-multiload/

Note that I use this in the gnome-panel (below) rather than that indicator bar that it at the top.

Since I have disabled this multiload-indicator, the problem has not happened once.