I spoke too soon. Bug has returned (the joy of intermittent bugs).
Message in syslog (cut and pasted from above comment because it's the same)
'kdm_greet[5332]: Internal error: memory corruption detected'
No messages about ~/.face.icon file.
Going into 'K' -> 'System settings' -> 'Login Manager' -> 'Users' (Tab) and deselecting 'Users - Show list' tick box didn't have any positive affect on the bug.
I spoke too soon. Bug has returned (the joy of intermittent bugs).
Message in syslog (cut and pasted from above comment because it's the same)
'kdm_greet[5332]: Internal error: memory corruption detected'
No messages about ~/.face.icon file.
Going into 'K' -> 'System settings' -> 'Login Manager' -> 'Users' (Tab) and deselecting 'Users - Show list' tick box didn't have any positive affect on the bug.