Apple Hardware Test (online) seems to have stopped without finishing.

[deckeda]

Got it restarted from the USB to erase the HD. Disk Utility shows the correct name for the HD, instead of "Mac OS X Base System".

But it will not erase the disk this time. Says, unmounting disk, erasing ... but just hangs now. Force-shutdown again.

NOPE! It just snapped into action, Operation Successful. Next up: Another Internet Recovery OS install attempt.