Q: The update completely screwed up my computer! Now it won't start-up - it only goes into Terminal then shuts down. After three tries Techtool Pro opens in e-disk mode to repair the problem (which it can't find a solution). Great Apple - thanks !

1. No, just you!
2. I hope you have a backup.
   1. Your hard drive may be about to fail.
3. Sounds like your computer is booting into single user mode, not the Terminal. Here is a reference about how to fix it: What to do when a Mac always boots to verbose or single-user modes | MacFixIt - CNET Reviews
4. I'd try to boot into the recovery partition and repair your hard drive.
5. Then get rid of Techtool, you don't need it.

Boot to the Recovery Volume (command - R on a restart) or hold down the option key during a restart and select Recovery Volume. Run Disk Utility Verify/Repair and Repair Permissions. Then reinstall the OS. As long as you don't erase and reinstall, all your other files should be there.

OS X Recovery

OS X Recovery (2)

Boot up holding down the Shift key and see if it boots into Safe Mode. If it does, you have third-party startup items that are causing it to crash. You'll have to figure out what they are and remove them.

1. None of my several iMacs, MacBook Pros or MacBook Airs have been "screwed up" by the update.
2. None of them have "Techtool Pro" or any other, similarly worthless programs often responsible for problems such as this.

Of course this must be some kind of wild coincidence.

Troubleshooting: My computer won't turn on

Read and follow all the steps.

1. Uninstall Techtool Pro.
2. You're welcome.

For insure that that there is no hardware issue that

could be the cause, run Apple Hardware Test.  If it

passes, at least you will have the piece of mind that

the hardware is good.

Apple Hardware Test->http://support.apple.com/kb/HT1509

If this gives positive results, you may want to give a PRAM reset

a shot.  This forces the Mac to reidentify all hardware and pass

that info on to the OS.  It may be possible that there may have been

some sort of corruption.

The fact that this is happenning so soon in the boot process

tends to lead one to believe there may be a hardware issue/

driver conflict/driver corruption.

BTW, what is shown in the lines of text displayed before reboot

(if it is there long enough to catch anything of note)?

What was the result of booting into Safe Mode?

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.

I don't think he's going to like your advice. He has rather strongly held opinions.

"I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it."

George Bernard Shaw