Dear Tom:
Sorry to hear about your dead queen.
I have been using MO in all my colonies and have not lost any queen(s) in any of
the
treated colonies.  It is possible to kill bees with MO ( I have warned about that
possibility) but you should not lose any by applying the oil in the form in which
 
describe the application.  The queen could have been balled by her own bees
if they became stressed after one of your inspections or might even been injured
during an inspection.  I would disregard illnesses because you mentioned only the
 
queen of two adjacent colonies.  Should it be illness you would have seen dead
workers and drones as well.
I am curious.  Please let me know if you notice any other signs.
Best regards.
Dr. Rodriguez
Virginia Beach, VA