Anyone seen this? I'm not sure of the circumstances that got me here, but I now can't adjust either of the backlight buttons for battery or power.

As you can see, both buttons are 'greyed out' and tapping them just produces beeps.
I tried a hard reset, and this returns the buttons to normal operation, but when I do a full system restore from my last backup (just before the hard reset), I'm back to where I started.
I'm thinking it might be a registry entry somewhere, but I thought I'd ask around here before playing with selective restores, or rebuilding from scratch.
Thanks.