This backlight issue is becoming famous among Macbooks. I have replaced half a dozen in the last six months, but luckily I haven't had a failure due to faulty logic boards. I know it is not really a fix, but using an external display will allow you to use your Macbook. It does, however, contradict the point of having a portable computer. Update: These 'toys' are such a hassle. I doubt if it is a logic board breakdown. It is more likely to be an issue with the inverter cable and/or incorrect installation of the new display. You must replace the inverter cable, the display and check all connections before blaming it on a logic board failure.