Backlit Keyboard -- Dead?

EDIT: Ok, this problem went away after I restarted. It let me use F10 to adjust brightness, and things are fine now.

I don't leave my computer on very often (I shut down / started up just 5 hours ago). If it's a factor, I unplugged my computer from the AC adapter while it was running. I have 10.3.5. Any ideas why the backlighting wasn't working?

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Okay, I'm not panicking yet, but lately my new (Rev C, 1.5GHz) Powerbook hasn't had the backlit keyboard come on.

I know it has the backlit keyboard, and I know it worked fine in the past (I've had it on).

I checked System Prefs > Keyboard, and it's set to come on in low light. When I press F10, I get the window in which you adjust the backlit keyboard's brightness, but there's a white circle with a diagonal bar through it at the bottom.

Any thoughts? Is it even possible for a backlit keyboard to go out? Am I just doing something wrong?
:confused

Oh yes, it was definetely dark enough. 🙂 The room is just about pitch black.

This happened again tonight. The screen doesn't dim and the keys just don't light. The room is completely dark, so I can't imagine what the problem might be?