could not write bytes broken pipe 3.2.0-74 3.2.0-72

[Galen Thurber]

I have two xubuntu computers with similar problem
https://answers.launchpad.net/ubuntu/+question/259325
https://answers.launchpad.net/ubuntu/+question/259025
One is a desktop and the bug happens with kernel
3.2.0-74-generic
while kernel
3.2.0-72-generic is ok
Xubuntu 12.04-current
memtest ok
disk test ok
grub is xubuntu installed
splash is disabled, verbose is on,

Second is a laptop
3.2.0-74-generic is unstable
3.2.0-72-generic is unstable
Xubuntu 12.04-current
memtest ok
disk test ok
grub is xubuntu installed
splash is disabled, verbose is on,
laptop runs LinuxLite2.0 and Sparky without this error

I'm stating this bug report from the desktop.
apport on this machine is also unstable, it crashes often

The broken pipe error appears before lightDM finishes take over of screen and on reboot.
sysreq screen out is not accessable due to no console being available.
Tried sysreq inside a logged into console but nothing seems to be logged once a console is opened and reboot is initiated from inside user's Xfce.
Note: reboot & shutdown under login screen are not working if kernel 3.2.0-74 is booted. -72 works fine

I've been checking dmesg output.

Once the system shows the broken pipe error (which seems to be 10/10 boots) the system becomes unstable in time
resulting in at times a kernel panic with keyboard LEDs

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: lightdm 1.2.3-0ubuntu2.5
ProcVersionSignature: Ubuntu 3.2.0-72.107-generic 3.2.64
Uname: Linux 3.2.0-72-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.0.1-0ubuntu17.8
Architecture: amd64
Date: Mon Dec 22 10:05:21 2014
InstallationMedia: Xubuntu 12.04.2 LTS "Precise Pangolin" - Release amd64 (20130213)
MarkForUpload: True
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)