Keyboard & screen back lights pulsate

Question

I have a MacBook Pro 15" early 2008 running !0.5.8. Tonight the keyboard illumination began pulsating bright-dim-bright-dim. At the same time the screen display began pulsating, too, sometimes alternating with the keyboard, sometimes in unison and sometimes unconnected, it seemed. Trying to control the keyboard light with F5 & F6 keys only showed me the usual semi-circular display blacked out with a little prohibition symbol underneath (circle with a diagonal line in its center). I tried the following remedies without any result.
rebooted
reset PRAM
repaired permissions
ran Preferential Treatment
reset SMC
Then I unchecked the automatic dimming control for both keyboard & screen. Now the keyboard continues to pulsate but at avery dim level. The F5 & F6 controls remain as before. The screen however does not pulsate. That is where I am at this point.  I suspect I may have to reinstall the OS, because there are one or two other software problems, but I'd be grateful any guidance possible on this problem.

Answer 1

The function keys change the range over which the level of backlight changes, Martin, but it is still varied according to the ambient lighting.
It is a tricky process in some ways. In a pitch black room, for example, you don't actually need the keys to be a as bright as you do in a room with "half light", for example, so it is not simply a question of the lights getting brighter the less light there is in the room. You will see that if you reduce the amount of light in many situations (stick your hand over the top of the screen where the sensor is, for example), that both the screen and keyboard illumination dims for this reason.
Cheers
Rod