What causes curved red lines on the display of Sony rear projection TV?

We have a Sony rear projection HD TV. It has worked fine for 5 years. Recently, we noticed that there are curved horizontal red lines etched permanently across the display. Regardless of the input we are using (dvd player or cable box), these red lines are permanently displayed when the TV is turned on. Any... show more We have a Sony rear projection HD TV. It has worked fine for 5 years. Recently, we noticed that there are curved horizontal red lines etched permanently across the display. Regardless of the input we are using (dvd player or cable box), these red lines are permanently displayed when the TV is turned on. Any ideas on what causes this and how to fix it? Is it something to do with cleaning some components?
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