OS X :: Snow Leo. Upgrade: Screen Not Working At All

I tried searching for 2 hours here and on google but nobody seems to experience exactly the same problem as me.

I upgraded to Snow Leopard. I got the problem alot of other people has been having: The screensaver kicked in during the installation. But I read about this after I turned off the computer by holding the power button which means I must have turned it off while it was installing.
Booted again and nothing on the screen. I got the chime but the screen was completely black(the flashlight trick didn't work, so the screen was totally off).

However it managed to finish the install after I turned on the computer again with the SL disc in the drive and giving it some time. It rebooted by itself and booted, this time with the screen on.

It booted up perfectly into 10.6 and I was happy. I thought I might just as well upgrade to 10.6.1 while I was at it, so I opened Software Update, downloaded the update and went ahead. I didn't reboot before doing this so this was done almost straight after it booted up in 10.6 the first time.

As far as I remember the screen changed to the 'starry sky' background while preparing to install and reboot.But now I'm stuck: I'm back to where the computer boots with only the chime. I can hear that the fans, hard drive and disc drive works. More or less everything else but the screen turns on.I've tried the flashlight trick again with no luck.I tried turning it off, taking out the battery and holding the power button for 10 seconds.I tried resetting PRAM by holding option, command, r and p when turning the computer on.
I tried holding down shift while booting.I tried holding down C while booting with the SL disc in the drive.

Nothing worked!

Right now when I turn it on it seems like it boots into OS X(the keyboard light turns on). Then it turns itself off after 5 minutes, then wakes again 5 minutes after that... And just continuing this cycle.