Boot the OS DVD and see if the issue continues. We don't need to do anything but boot the OS DVD. We are not looking at reinstall or answering ANY question to that boot. We only want to boot the OS DVD and see if the pulsing continues.
If it does then your laptop needs repairs.
I have a MacBook Pro 15" early 2008 running !0.5.8.
Last night 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.
ran Preferential Treatment for system preferences
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.
Has anyone had experience with this? I suspect I may have to reinstall the operating system as there are some other irregularities from time to tim,e.