My toshiba u400 the screen goes dim

hi.
i have a toshiba u400 when i turn it on the screen goes dim after it loads, the screen is bright untill the window symbol has finished loading the goes black.if you cup your hands and peer into the screen you can see the programs are working.is this a hardware problem ive been told it could need a new screen or inverter is this true or have you got any ideas?