Comment 2 for bug 116107

i don't know if this helps, but i think i have narrowed this down to the asus_acpi module. steps to reproduce:

1) boot up in recovery mode
2) confirm that Fn+F8 works for display switching
3) modprobe asus_acpi
4) confirm that Fn+F8 does not work

this module caught my attention because it was one of the ones that was newly loaded between the recovery mode boot and running /etc/acpid start. i haven't necessarily rules out all of the other modules, but there is a very short list of realistic culprits.

the strangest thing to me is that unloading that module, and any others that were loaded because of it, does not return the system to its previous state where Fn+F8 works again. my best guess is that loading this module triggers a change in kacpid, the kernel daemon, but that it this change is not reverted by unloading the module.