(system is unresponsive and just sits there, pressing reset doesn't make any difference)
If you hold down the power button, the system should turn off after several seconds. Then power on again, and tell us if it boots normally (and if not what error message you see).
USB recovery of a Legacy system running OS6 is always going to fail, as it will not find a compatible platform. When you use the renamed system, it sounds like it's failing at another place, unable to find a compatible image. And the Telnet is likely an undocumented feature of that -- possibly looking for a compatible image via Telnet. I've not looked into the initilization file enpough to see what happens in that case.
If I'm right, then it's still running off the system from the USB, not the one in flash; but I suspect the environment is very similar, if not exactly the same. It certainly seems worthwhile to try.
The Ultra6 does have a VGA header on the motherboard (at least, it's labeled as such and has the right number of pins), though I have never connected to it and do not recall seeing confirmation here that it is of standard configuration. But Netgear tends to be pretty consistent, so I suspect that it is (as it is on the 6-bay Pro models). With a proper cable, you could look for BIOS and boot messages to try and diagnose further.
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