As per standard practice, unplugged all household electronics before going on holiday. Came home, plugged everything in, and no joy whatsoever from the Motorola HDPVR. Did multiple power cycles. Including unhooking the cable connection itself. Phone and internet work perfectly, so it's definitely an issue with the PVR. On power cycle, it just goes to "boot", stays there a while, then turns itself off. Pushing the "power" button on the remote stalls out at the little "beachball" equivalent on the screen, but with no motion/activity.
On a couple of power cycle attempts, it flashed something like "OCAP loaded" (or completed or something similar) part way through the process.
It definitely gave the "Login Failed" message.