autologin fails after power up at wall

I thought I would be able to get some resolution via #1250875 but although " 2015-03-14:
Status changed to 'Confirmed' because the bug affects multiple users'"
it is unassigned, and my inputs to it seem to go unheeded.

What happens to me under 14.04 is that when I start up the PC from no power at all, with my account set as autologin=yes I see my desktop (but without the mini icons at top right) for anything from a blink to five seconds, then I am sent back to the login screen (aka unity greeter??).
If I arrow down to the other account, the background shown is as for that account, whereas my account displays the standard purple and white dots (<- also if I remove autologin).

And if I switch autologin to the other account, autologin works from power up. My BIOS is set of course to "resume after AC power restored".

It seems fairly clear that some sort of fault has developed in one or more files associated with my account. For example, what file or files does greeter access (a) to know which desktop background to show (b) which if any account has autologin=yes

I am reluctant to delete and recreate my account, though tempted to bomb and clone to 15.04. It's a long process including setting up mythtv etc etc etc again.

This fault BTW does NOT occur when doing a warm restart ie shutdown then hit the power button to restart but DON'T power off at the wall, so the PC power supply maintains power to the motherboard.

I'm asking this as a question because it is perhaps not a bug as such, but the result of a corruption in an account file.

You need:

lsb_release -rd
Description: Ubuntu 14.04.2 LTS
Release: 14.04

Is this a lightdm issue? If so, you might want:

apt-cache policy lightdm
lightdm:
  Installed: 1.10.5-0ubuntu1
  Candidate: 1.10.5-0ubuntu1
  Version table:
 *** 1.10.5-0ubuntu1 0
        500 http://au.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.10.0-0ubuntu3 0
        500 http://au.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

What I expect to happen is that if autologin=no greeter shows me my normal desktop background (trivial) but if autologin=yes then autologin happens!!!!!!! WHEREAS if I restart without powering down at the wall, autologin succeeds.

As already explained, if autologin=yes my desktop is shown very briefly, then the screen reverts to the login screen with default background. The default background is a trivial issue, but perhaps a useful diagnostic, as it shows greeter is NOT getting the usual account info.

Thanks VM. This is not a drop dead one, but is annoying!