What happens if you menu+select then switch quickly to just long-hold menu? Can you get thus get it into OF mode? And then copy rockbox onto it?
Or if you menu+select then switch to menu+play, which should get it into disk mode (then copy rockbox onto it).
What happens if you do [long] menu+select while it's connected to the computer, does iTunes then see it as an ipod that needs to be restored?