Thanks for the replies guys. As a last resort I tried a different computer and using instructions that I got from Line 6 tech support my Helix is back, thankfully. For others I’ll post their instructions here, maybe they help someone else out in the future:
Noted. Wasn’t aware that one particular USB cable might work with one device but not the other. That’s really good to know, thanks!
You are completely right. I had kind of made this my personal rule and I don’t know what made me do the update...
As for "attitude adjustment": You may be right. But I don’t see that this is a case of user error and we can probably at least agree that it would be desirable if the update process was less risky, can’t we?