Comment 6 for bug 994306

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.