24" LED Cinema display still flickering after firmware update.

24" LED Cinema display still flickering after firmware update. Display was flickering on and off every few seconds, which also affected the display on my iMac.

Did a search and found the firmware update to resolve flickering issues. Determined that the firmware on my screen was not up to date. Tried to run firmware update when the display was plugged into the Thunderbolt port on my mac, but because it appeared to be disconnecting and reconnecting, would always fail. I then unplugged the Display cable and left the USB cable plugged in and it would still see the display, after three attempts it actually updated the firmware successfully. I then unplugged the display from power as per instructions and then plugged everything in.

Then Success....breifly, the screen worked flawlessly for about an hour then reverted back to previous behaviour.

Any ideas on why it worked at all and then stopped?.