I have not been able to find a solution to this exact problem.  Seems like it is either the power inverter or the backlight on my Latitude D830.  My screen gradually grows dim on the right half to 2/3 of the screen.  Seems like the longer it runs, the darker it gets.  Works fine hooked up to a monitor or HDTV through the docking station.  This is a 17" screen, so its possible that there are two bulbs and one is going bad.  Or it could be a bad inverter.  But if it were the inverter, wouldn't the whole screen be affected?

Thanks in advance!