emulatorII-list

Excellent thorough post Martin; you are certainly checking all the
right things.

Did you take a hard look at everything on the Mac end (AppleTalk,
network/port/communication settings, possible file corruption, etc)?
You mentioned the Mac can be slow starting up; are there any problem
extensions loading (or required extensions failing)? Might you have
access to a second Mac (or E-II) to swap in?

Good luck, wish I could be of more help.