KDE backlight control - backlighthelper not running?

[Maciek Borzecki]

I'm seeing an odd issue with KDE and screen backlight control. I'm
running Thinkpad T60, with KDE 4.7 (from updates) and unfortunately
the backlight control does not work. Pressing Fn+Home/Fn+End does not
seem to have any effect. I normally have to tweak hotkey mask to
something like 0xffffff in order to have the proper key events appear,
and it does work but only in Gnome and Xfce.
Before anyone suggests reinstalling bash, I've already done it
(otherwise it wouldn't work in Xfce).

Looking at the logs:
- kded debugs:
kded(2495) PowerDevil::BackendLoader::loadBackend: Loading UPower backend...
kded(2495) PowerDevil::BackendLoader::loadBackend: Success!
kded(2495) KDEDPowerDevil::init: Backend loaded, loading core
kded(2495) PowerDevil::Core::loadCore: Core loaded, initializing backend
kded(2495) PowerDevilUPowerBackend::brightness: Screen brightness:  0
<---- why is current brightness 0?
kded(2495) PowerDevilUPowerBackend::init: current screen brightness:  0
kded(2495) PowerDevilUPowerBackend::init: Can suspend
kded(2495) PowerDevilUPowerBackend::init: Can hibernate
kded(2495) PowerDevil::Core::onBackendReady: Backend is ready, KDE
Power Management system initialized

- messages - nothing about backlight helper being activated
- .xsession-errors - nothing related

Since it does not work with 4.7 from updates, I updated to 4.8 from
kde48 repo. Unfortunately, with similar results.

As a last resort I checked with KDE live spin, and amazingly,
backlight control works. So something between the current version of
packages and the one from live KDE spin, things got broken.

Correct me if I'm wrong, but looking at the code, I see that in order
to control the backlight, there's a helper program
(/usr/libexec/kde4/backlighthelper) which starts through dbus
activation, and exposes brigthness, setbrigthness methods. I take that
once started the demon should remain running at lest for some time.
Now in KDE spin, that happens to be the case, I can clearly see
backlighthelper process listed in ps output (there are also logs in
messages, that activation of backlighthelper was successful).
However, right now, no such log is to be found, as if for some reason
backlight helper does not get started.

Any ideas on how to proceed with debugging this?

Thanks,
--
Maciek Borzecki