UPDATE: It only took the Apple Store 24-hours to report that my MacBook Pro has been fixed. They believe it was all software related. They were able to reinstall the latest system software, and after the new update the computer appears to be operating normally. The drive did not have to be wiped clean, so I avoid having to restore from the latest backup. We will see. I’ll pick it up tomorrow and give it a test drive or two before declaring victory.

You know it’s bad when the guy at the Genius Bar in the Apple Store plugs your computer into their diagnostic network, presses the power button, watches the screen carefully and then, puzzled, calls over the next genius to look at the screen.

“Have you ever seen that message before?”

First diagnostic test–wouldn’t run.

Then he tried to boot into the built-in hardware test. I did this same test just before we left for the mainland. It ran and reported no hardware issues. This time around the screen turned black, the test started, then almost as quickly stopped. A second try brought the same result. It wouldn’t run through the whole test.

At this point, he said there was an unusual error message, something about not being able to find a serial number on the mother board. That’s the mother board that was replaced back in January.

Third approach was to boot from an orange, ruggedized La Cie drive they keep on hand for such cases. When you think the problem might be with the computer’s internal drive, you try to start-up with an external drive. This would then allow you to examine and perhaps repair the presumably faulty internal drive. But, as I had found at home, it got as far as the blue screen and stalled.

The external drive went back in a drawer, and at this point Apple’s genius began writing a description of the diagnostic steps to pass on to a technician. He booted the computer one more time in order to be very clear on just where it would stall out. And this time it worked, as if there weren’t a problem at all. Just like earlier today, when it worked started up properly about twice out of a dozen times.

Needless to say, they expect it will take at least a couple of days to figure this one out.

Because this all started with the upgrade to the latest system software version, a corrupted hard drive seems to be the natural suspect. But the failure to boot from an external drive would seem to contradict that assumption. So I have no idea what they’re going to find.

Luckily, I did a full backup before doing the software upgrade to the latest system that triggered this whole episode. And, still lucky, I’m able to put an older laptop back into service for a few days while the diagnosis and repair is completed.