For anyone keeping score (or using SEARCH), this issue eventually got resolved. The ethernet chip had D5 (Data line 5) stuck low for some reason. I disconnected it, and the rest of the player came back to life.

Details in this thread

EDIT: I suppose it even makes sense, as the player had been reporting Could not find CS4231A (version=80) , whereas the true version of that chip was a0, which is 80 when you force D5=low (0).

-ml