Lesultan wrote:
Now is there a chance you could find another moment to explain WHY TTP is such a problem ? I've used it for more than 10 years and it's only been an asset.
I realize you considered my response unhelpful, but my answer remains unchanged: uninstall it.
You explained that your Mac was unable to start. In that case the Apple Support article is the appropriate place to begin troubleshooting.
You also asked if anyone else had been similarly affected. Lacking an overwhelming response from a representative sample of millions of Mac users running the latest OS X release, any premise that the update caused this problem must be logically flawed. On the other hand OS X updates will very frequently reveal incompatibilities with third party software, especially those that modify the Mac's operating system. Techtool Pro is one of many that do.
TTP is also unnecessary in that it conveys no benefit. An example is the following: http://www.micromat.com/support-45/knowledgebase/ttp7kb/techtool-pro-has-found-b ad-blocks-what-do-i-do7
Solution: erase the volume, if it happens again replace the drive. Really?
TTP and similar utilities may be used to "repair" a damaged HD for the purposes of extracting whatever data remains intact, after an irretrievable data loss event has already occurred. Your very complaint illustrated that it was unable to do that. Conclusion: it's worthless.
... I decided to run the Mac Pro in Target Disk mode and run Disk Utility from my laptop on the suspect disk - it repaired (or so it says) the disk and now I'm copying ("restoring") all contents onto another disk that I can run further tests on later.
To be clear, Apple's Disk Utility accomplished what TTP could not.
Most likely, your HD is already in a failed state, so I don't recommend relying upon it. I do recommend that you extract its data, then replace the drive.
A failed HD will fail again, every time. Hard disks are cheap, and backups are essential. Having a reliable backup strategy makes events like this a non-event. If you want to keep the HD in service despite these cautions, I recommend you erase it as recommended by Micromat, do not reinstall TTP, and if it fails again replace it - also as recommended by Micromat.
I maintain many Macs for many people and have done so for many years. None of them have TTP or any similarly clever utilities installed. It's your Mac, do with it what you will, but if you choose to install such junk you own the consequences, which may be that it trashes your Mac.