I have a similar issue. Difference being I can see and use the external hard drive (connected via SATA connector) for about an hour, after which it is no longer accessible. Have to power down the Q5, then turn power back on. That will allow me to use the drive again for about an hour.
I am using a 1.5tb 3.5 inch hard drive, connected using the Q5 included SATA cable and port.