Sleep light problem

I purchased my 24" Imac back in January 2007. In the right hand corner of the monitor, there is a white light that glows on and off when the computer is sleeping. Previously, when the computer put itself to sleep after 15 minutes, the light would automatically start glowing on and off. Recently, this light stays on when the computer is in sleep mode. The light will only glow on and off when I select sleep from the Apple menu.

I tried calling techical support and they gave me the following fix for the problem:

First shut off the computer and unplug the power and other cords from the computer. Wait one minute.

Plug the power cord back in again along with the other cords.

Then push the On button and immediately push the following keys simultaneously while the computer is booting up: option key, apple key, P key and the R key. Hold these keys until the computer has rebooted twice (you'll hear the sound it makes starting twice).

I had this same problem with the sleep light about 9 months ago and this fix did the trick. However, I tried it again the other day several times and it didn't work. The Apple tech told me over the phone that there's a glitch in the computer and I need to take it to an Apple store to fix it. Does anyone have other ideas about how to fix this problem? Thanks!

 

I have not changed the energy settings at all since I got the computer and it has gone into sleep mode with the screen going black and the white light glowing on and off for the past 9 months. I have checked the energy settings and the computer is set to go into sleep mode after 15 minutes. The screen is still going black after 15 minutes, but the white light stays on. The Apple tech assured me that the computer is going into sleep mode, but he thought there is something wrong with the computer that is keeping the white light on.