Comment 13 for bug 173682

OK, I'm going to have to go with the assumption that xorg is the problem here, since that is what's eating your CPU, and the problem doesn't seem to be based on any other applications being running. Now I need you to collect some detailed data:

Log out of your current session.

Press Control-Alt-F1 to enter a text terminal, and log in there,

Stop the display manager. If you are using Kubuntu, this should be done with
sudo invoke-rc.d kdm stop
If you started with an Ubuntu installation, you may still be runnning on gdm, so that would be
sudo invoke-rc.d gdm stop

enter the following commands:
sudo dpkg-reconfigure xserver-xorg
uname -a > uname.txt
lspci -vvnn > lspci.txt
sudo discover --disable=parallel,serial,usb,ide,scsi,pcmcia --format="%M\t%S\t%D\t%i\n" video > discover.txt

Attach to this bug report the files created above (uname.txt lspci.txt and discover.txt) as well as /var/log/Xorg.0.log and /etc/X11/xorg.conf