Originally Posted by knc1
Might be another case of a battery too discharged.
Put it on a charger (not in fastboot or diags mode - it doesn't charge in those modes).
Actually, if you monitor the serial port status messages while connected in fastboot mode, you will see that it charges quickly in fastboot mode (with periodic status messages showing battery voltage).
Diags mode on the other hand is notorious for discharging the battery to unhealthy levels that can be difficult to recharge, perhaps making it appear to be bricked.