Two weekends ago I had to return back to Apple Harvest HQ from my girlfriend's house to sort a few things out and to pick up some forgotten bits and pieces.
On the Sunday morning I booted up the MacBook Air for the first time since I'd arrived since I'd been using the iMac exclusively over the course of the weekend. Well, I tried to boot it up but it wasn't having any of it. The Apple logo would appear, then the start-up chime would sound and the spinning gear wheel would start, all as normal. Then the screen would flicker and the gear wheel would change appearance slightly before stopping completely. The screen would then flicker again, changing colour slightly, the wheel would spin a bit more and so on. But it wouldn't boot.
I tried rebooting in safe mode and although the safe mode progress bar would appear the result was the same. Boot failure. For the next hour, I tried every trick in the book. I cleared the PRAM, SMC, ran the internal diagnostics (no issues!), reinstalled Mavericks through booting up in recovery mode but nothing worked. The disk utility checks also indicated that the flash drive was OK. I had been thinking the worst - that this was a major hardware failure and was likely to be very expensive (although the MBA is still covered by Apple Care until next July) - but if the logic board had failed, or the video was knackered, then I wouldn't have been able to run any of the utilities or reinstall the OS.
I had a Time Machine backup from the previous Thursday so I decided to restore this as a last resort. It worked, and I've not had any problems since.
This last weekend I went back to HQ again to check on things. I've been remotely connected to the iMac via Slink but noticed that one or two updates had failed, so I decided to reboot the machine and try again. And guess what...Yes, exactly the same scenario as with the MBA. Complete boot failure under every attempt. The only difference on this occasion was that under the dual screen set-up, the extended display flickered rather than the main iMac display.
In this instance I was unable to fix the iMac - for some reason, Time Machine has not been backing up to the 3Tb Time Capsule for the last month so my most recent backup available was pre-Mavericks. However, I did clone the disk as a precaution should I lose the connection to the iMac from Mel's house. Sadly I didn't have it with me this weekend, and I also ran out of time, so I'm hoping that a clean install of Mavericks and a restore of the cloned disk will end up getting me the right result, namely a fully restored iMac.
How extraordinary that two different machines, with completely different configurations should fail in exactly the same way within a fortnight of each other. Coincidence? I doubt it, but I'm stumped as to the root cause. I can only guess that some installation or update of something has caused it - but it's now impossible to narrow it down. I've not seen the message boards or forums awash with this specific problem, although I have seen some similar instances, but no pain free solutions or root causes.
So, until I get home next week, there's nothing I can do except sit and wait, and hope that my proposed fix will work - note to self...remember to take the clone disk home and not write over it in the meantime!!!!!