Backlight on MacBook doesn't work

Hi,

I have a really big problem with my Macbook 13". Before I went sleep, I've been watching movie. Then I've closed it normally but on another day the backlight doesn't work anymore. When I plug in external monitor, everything is okay (apart from MacBook's screen of course). Interesting thing is, that when I completely turn off the light and then I turn it on, it lights for a few seconds (sometimes more, sometimes less seconds). I've been searching everywhere and found a lot of people with the same problem but I just can't resolve it. I'm not sure if it is a hardware or software problem...

Any ideas where is the problem?

Thanks for help.


Sona