Okay,

First of all Mark, I'm sorry if anyone gave you a hard time, your steps are actually quite clear and it was I that misread them. I also appreciate that you do know exactly what you are talking about. Unfortunately these still have not solved the problem.

Reflashing Hijack hasn't worked.
Reflashing the original kernel from the Hijack site works.
Reflashing Hijack after installing the original kernel from the Hijack site still results in the same error.

I haven't yet tried the developer software version. Should I?

Hijack is installed, and I can enter the menu. I did not however find anything re HD Settings. Is it under another heading in the Hijack menu or is it therefore missing and could that have anything to do with the error.

A few anomolies for you:

Even though I installed the Hijack Kernel with the "boot with Rio personality" option chosen, the player still boots as Empeg with our little penguin friend.

Whilst I was in the process of checking this thread, I realized that if left long enough, the error message actually disappears and the player 'appears' to be fully functional including the Hijack menu. So is it just a glitch that I should ignore?