The poroblem can either be the 12~18vdc power supply section is not supplying the power to the backlight inverter board or the inverter board went out, you need to check voltage on the power supply, also look to see if you see any caps with leaking/bulging top.
See example of failed TV and monitors here:
http://s807.photobucket.com/home/budm/allalbums
http://en.wikipedia.org/wiki/Capacitor_plague
http://www.badcaps.net