I have a peculiar situation. A month back my display suddenly froze (without any prior issues). It started giving 8 beeps sound. As I learnt from different threads, it looked like LCD issue. My system has a dual boot (Ubuntu and Windows). I tried connecting to an external display. Windows display was very jarred (unreadable). But when I tried the diagnostic test, the screen somehow came back. I had to update the GRUB, then the system started behaving without any issues. It lasted for a month. Then I again hit the same problem.
I tried reseating the display cable and do a display test...nothing worked. Display test shows extremely faint colors on the screen which are extremely faint to be noticed easily. Diagnostic from external display also did nothing this time. However I could log into Ubuntu using external display. And if I select restart on the external display, while restarting the LCD screen would turn on and work perfectly fine (for hours without a glitch) until I do a shutdown. Now every time the screen does not come up after shutdown, I have to reconnect to an external display and then order restart to wake the LCD up. And this works !! Although many times it will come up after shutdown without any issues too and Display test is fine too (bright colors).
So, I do not think the problem lies with the LCD or cables or video card.. I am puzzled. Any help will be appreciated.