Help! Screen Backlight Recently Failed for Roughly 30 min.

I have owned this computer since 2006 and it has had no problems. I recently replaced the hard drive myself (using 2 screwdrivers and an iFixit guide) and the computer worked perfectly for about a week.

However, last night as I was using the computer the screen suddenly (and without warning) went black. Further investigation revealed that the backlight was not functioning at all: I could shine a flashlight on the screen and see things just fine; I could manipulate the volume settings; and I could restart the computer and have it boot and run programs perfectly, just without any backlight to the screen. Also, during the entire time the computer worked perfectly with an external monitor. I tried resetting the PRAM and also performed a reset by taking the battery out of the computer, unplugging it, and holding down the power button for 5 seconds. I also booted the computer into safe mode. Unfortunately, none of these fixed the backlight issue.

After roughly 20 - 30 minutes, the screen miraculously came back on! As I sit typing this, the screen has been working flawlessly since last night. However, I'm very concerned about this happening again.

Any help would be greatly appreciated.

Thanks very much.

-Charles

P.S. I'm running OS X 10.5.8.