Stupid F7 boot loop

[Jonathan Allen]

Hi All,

I have a stupid F7 box that won't boot.  It keeps wittering about a clutch
of selinux errors:

  udevd-event[1187]: selinux_setfscreatecon: matchpathcon(/dev/loop3) failed

and screenfuls of similar garbage.  Then it tells me that an error occured
during the file system check - which it didn't.  I give the root password
and run fsck and there are no errors.  Reboot simply goes back into the
same loop.  I can't edit /etc/selinux/config to disable selinux because the
filestore is read-only and the live CD doesn't seem to want to let me mount
the hard-disc to edit it that way.

How can I return the machine to some kind of sanity without reinstalling ?
This feels scarily like the monster from Redmond ...

Jonathan