Ralph Barron this from the manual:
6X Blink - Backlight System Failure
If the inverter circuits fails to generate high voltage or one or more of the backlight lamps fails to light, the television will shut down and display this diagnostics error. Observing for the presence of backlighting is crucial in determining which component is likely at fault.
If the backlights turn on before the 6X shutdown occurs, it is safe to assume that the inverter circuits are functioning and one of the lamps failed to ignite. Replacing the LCD panel is necessary. If the backlights never turn on before the 6X shutdown, the inverter has failed. If the inverter is available for replacement, replace the inverter. If the inverter is not available, replace the LCD Panel.
Do not replace the panel yet ;-) but start with the inverter. Here is what they look like as well as an idea about the price. If you have trouble finding it, post some images of your board etc. with your question so we can see what you see. Use this guide Adding images to an existing question for that.