The symptoms of this issue seem to be the same as those in Bug #698121. I found the same error output in my Xorg.1.log file:
Fatal server error: [250852.257] xf86OpenConsole: VT_WAITACTIVE failed: Interrupted system call Bug #698121 is indicated as affecting the xserver-xorg-video-ati package. I do have this package installed, even though I have an nVidia card and I have not seen any mention of ATI hardware or drivers in this bug. Maybe the problem is more general than was previously thought? -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg-server in Ubuntu. https://bugs.launchpad.net/bugs/742517 Title: [sandy bridge] xorg freezes with 100% cpu usage To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/742517/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp