What does it mean when the USB power/fault indicator flashes blue?

A flashing blue USB Power/Fault Indicator means a fault condition exists (thermal fault, low battery voltage, overload, or short circuit). If the upper indicators flash blue, a fault exists in the first two USB ports; if the lower indicators flash blue, a fault exists in the bottom two USB ports. The USB ports will automatically shut down. Disconnect the device, press the USB Power Button to turn off the ports, and allow the unit to cool before trying again. Ensure device draw does not exceed 3.1A per port pair. (Page 14)