Having a photo of the bar in question would help, but probably 90% or more of the time that is a failure in the LCD panel. If you connect an external display to the laptop and you do not see the same bar on there, then it's about 99% likely to be the LCD panel having gone bad. The only thing that can be done is to replace the LCD panel, so if the unit is under warranty, now's the time to call up the manufacturer about setting up an RMA.