A blinking power LED just means that the software crashed. After a crash the LED blinks ten times, then the computer restarts. If it crashes during initialisation, it does this in loop: crash, blink, reset, crash, blink reset, ...
So your "one long blink" does mean nothing but that the computer restarts.
Usually the cause of the crash is shown by the color on the display (red, green, yellow). A black screen does not have a specific meaning. It might mean that something is dead on the motherboard so that it cannot display anything. Or that it crashes in a phase of initialisation which does not set a color.
