My fear that if I took it apart to find the cause, it would fail completely were realized. The car is now unstartable. But I found that the problem IS internal to the lock mechanism and not in the electrical part. (Turning the key does not turn the piece that moves the electrical switch.)

I was surprised to find that I cannot start the car using a screwdriver to turn the electrical switch, with the key in the lock. (I thought that the presence of the key would satisfy the immobilizer. But apparently not.)

Klaus, please elaborate on how I get a new lock assembly to match my existing configuration. Is this something that the dealer can get quickly? (I have to leave on a cross-country drive next weekend.) Or is it a long lead time, ship from Sweden item? If I have to buy a non-matching lock assembly, what are my options?