|This is not just a problem. i am also writing its solution.|
Problem :Toshiba laptop screen is just blank at all times when powered on.
Not all the times really. Actually after trying to switch it on several times,laptop suddenly switched on.
So i never shut down my computer. i just log off (once it started).
I checked battery (working fine).
Checked AC supply (working fine).
checked drivers (all perfect)
Solution: Just switch ON your computer in safe mode. Uninstall garphic drivers (in my case it was NVIDIA 200M). then install updated drivers if you have otherwise restart your computer normally.
I hope it will work out. as it worked out well for me