User accounts broken (in an odd state) since kernel panic in ML MBA 11" 2012 model, ML upgraded from Lion

User accounts:


admin
admin
normal user
guest


Working fine for a week or so. Was logged in as 3. (a regular user), and asleep.

When trying to resume the next day, it showed the desktop and just as it became interactive it crashed with a kernel panic - first one I've had.

At the login screen, where all four accounts used to be visible, now only 1. and 4. are available.

In the users &amp; groups system config dialog all accounts are present and look fine. I can log into accounts 2 and 3, but only if I switch user whilst logged into account 1.

Any ideas? Very confused and I don't know enough about how user profiles are built in osx to know what to look for.
Your first triage step is to isolate software from hardware. You could install ML clean on an external drive and see how it works or just erase your Mac and reinstall. Once you've concluded the hardware and base OS is stable, you can try the migration / restore from backup again or start narrowing down software corruption as a cause.

Assuming you can make the kernel panics happen - once you have 4 or 5, the stack trace should point to a pattern of where the system is having problems. If you can't reproduce the panic, then you may just need to clean up from a hard landing by restoring from a time before the unlucky crash.