Comment 5 for bug 1356134

Same issue confirmed...100% CPU load according to htop or SysPeek with to few processes/apps running to reach 100%.

Hypothesis: issue related to display (only that in activity) with CPU including IGP ?

Solution that worked fine for me (done 24h ago):

Install the driver Intel Linux Graphics avilable at https://01.org/linuxgraphics/downloads
(take the .deb "Graphics Installer 1.0.6 for Ubuntu* 14.04, 64-bit")

Start installing and you will have an error...normal (distribution not supported). To be able to install it, edit the "lsb-release" text file in the "/etc" directory and change it to this:

DISTRIB_ID="Ubuntu"
DISTRIB_RELEASE=14.04
DISTRIB_CODENAME=trusty
DISTRIB_DESCRIPTION="Ubuntu 14.04"

Run the installer again and there won't be any error now...reboot...the CPU will go back to normal load

I hope that will be helpfull