I don't have a Glo HD, on my H2O a regular boot sequence will see the power LED blinking on and off for a few moments until it stops. Is this similar on a Glo? If so, then it should mean the device is booting regulalry, but the display does not work anymore for some reason.
With a broken SD card or if the boot fails, it should either not start blinking in the first place - or never stop.