Saw this issue when installing Seagate Barracuda 1Tb HDD's into the unit. The drives would spin up and the four drive lights surrounding the power button were lit (showing the disks were recognised), but the power light would flash continuously. The unit never appeared to boot into an OS and it never negotiated an IP Address. I tried a factory reset of the device to no avail.
Ended up accessing the bootup console via the RS232 header and entered the BIOS setup. Found that the boot order for the unit was set to boot from the 4 drives first then the DoM unit. Re-ordered the boot list so the DoM was first and saved the changes. The unit then booted correctly.
I tried the Seagate disks in two different units and they both displayed the same boot issues. Changing the drives out for WD drives allowed the units to boot without having to update the boot sequence.
Since tried 500Gb Seagate Barracuda drives and they showed experienced no boot issues. I've yet to take a look at the boot order when everything is working okay to see whether it was something with the drives I was using.