Aug 23 2011

There Was a Problem Installing Mac OS X (Lion)

I had a couple of MacBook Pro laptops grace my desk and I have been upgrading them to Mac OS X 10.7 (Lion). The first one (maybe eighteen months old) went through without a hitch but the second one (which is a few years old) had all manner of problems including reading my original DVD-RW that I had burnt using the DMG file from the Mac App Store. Another significant problem I encountered was after the initial installation, I kept encountering the error…

“There was a problem installing Mac OS X”.

Quite non-descript and quite unhelpful and even a format and subsequent reinstall didn’t fix the problem.

What I discovered was that the setup for Lion seems to store data in the PRAM (Parameter Random Access Memory) and if this data is corrupted or becomes stale it becomes necessary to reset it in order to undertake a successful installation.

So how is it done?

  1. Turn off the computer,
  2. Hold down “Command”, “Option”, “P” and “R” on the keyboard,
  3. Turn on the computer,
  4. Keep holding down the keys until the computer restarts itself again (maybe ten or fifteen seconds at most),
  5. Release the keys after the computer has restarted again.

From here you should be able to proceed with the installation of Lion with no further problems.


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  1. Pino

    Thank you – this helped me

  2. fotomate

    finally it works. i couldn’t get through this error, bit now it works fine on my old MacBook Pro. thanks

    1. Boyd Chan

      Glad to hear! It’s certainly one of the more obscure and frustrating problems encountered with an OS installation.

  3. changyoung

    Oh my god! thank you!

  4. Charly

    Thx for the tip !

  5. Jo

    OMG! You are a life saver. Thank you.

    1. Boyd Chan

      No worries 🙂

  6. Elliot F

    The user had re-formatted his HD and couldn’t recover. Nothing else worked. 2 days. The recovery partition, Firewire target disk mode, DVD installer. After clearing the PRAM, installation is going now from a clean install DVD image.

  7. Michael H

    You ROCK! Didn’t know we had a “P” ram still. Thank you Soooooooo much

    1. Boyd Chan

      My pleasure!

  8. Martin

    Thank you so much.

    1. Boyd Chan

      Glad to help 🙂

  9. Chao

    Great tip, thanks.

  10. gandalf

    saved me, thank you very much!!!!

  11. Dave Kemsley

    There’s one more step to do this for those who have the firmware password turned on: turn it off.

    You can’t reset PRAM/NVRAM if the firmware is password protected.

    1. Peter

      Actually PRAM resets the Firmware password, you just have to either change a ram stick or temporarily remove it then reset the PRAM.

  12. Isra V

    Thanks for your help…Regards.

  13. Boris

    Thanx a lot!!!! Respect!)))

  14. FOX

    Thanks man!

  15. Marc

    Mines not working 🙁 have been having problems for a while so decided to erase the disk and do a reinstall. Only problem is I didn’t back up lion to an external drive. When I try and reset the PRAM it he machine is not restarting itself and I just end up back at the same screen with the same message 🙁 any ideas more than welcome

    1. Boyd Chan

      That is odd. Let me think about this and get back to you.

  16. Michael

    Awsome! You have helped me out (after 3 hours of reinstalling boot drives etc) – Big up man Go buy yourself a beer from me. 🙂

    1. Boyd Chan

      No worries at all 🙂

  17. James

    Dude THANK YOU! I’ve seriously been trying for a day to figure it out. Used two different hard drives and STILL was getting an error until resetting the PRAM. You’re awesome

    1. Boyd Chan

      It is such an annoying issue when you don’t know what is going on! Glad to hear you’re back up and running 🙂

  18. Magid

    Tried to up grade my mac book pro by installing osx mountain Lion ,keep receiving massage telling me the hard drive is damaged and cant be repaired, tried disc utilities trying to repair it doesn’t allow me tried to reboot using safe mood doesn’t work I don’t have extrnal device to reboot from can u help please
    Many thanks

    1. Boyd Chan

      It sounds like the drive itself might be on the way out but I note @ http://forums.macrumors.com/showpost.php?p=15349677&postcount=11 that someone used Alsoft DiskWarrior which did the trick for them to at least roll back to their prior version of Mac OS X. Seems as if Mountain Lion can damage the partition information but DiskWarrior can correct that bungle.

      Your mileage may vary and I’ve not used this myself but worth a shot before seeing an Apple Genius (if your Mac is under warranty) or buying a replacement drive.

  19. Toshlad

    My daughters MacBook HDD failed. I put an old drive in and it nearly installed but then the install hung. I thought the replacement drive might be suspect so went and bought a new HDD. Then I got the error above. I was nearly at my wits end and my daughter had given up hope of having her mac back. You saved the day. YOU ROCK!!!!! Thank you for your help.

    1. Boyd Chan

      My pleasure – happy computing! 🙂

  20. mustafa

    thnx vere much bro

    1. Boyd Chan

      No worries 🙂

  21. Kyle

    Hey man, you really rocks. I mean i have been beating my self up about this problem. A friend of mine trusts me so much that he brought this problem and i could not fix it in 4 days. I read your article and within few seconds, T’adaaaaa….I’m good. Thanks so much and i hope i could follow you on twitter or so..BTW…big ups.

    1. Boyd Chan

      It is a tricky problem but easy once you know how! If you want to follow me on Twitter my handle is @therealboydchan 🙂

  22. Donny

    Thanks, that’s very helpful

    1. Boyd Chan

      No worries 🙂

  23. Reza Arian

    Tanx-Tanx-Tanx-Tanx-Tanx-Tanx-Tanx-Tanx-Tanx-Tanx-Tanx-Tanx- 😉

  24. Steve Job

    Oh boy, for 3 days and now it’s that simple. Thanks!

    1. Boyd Chan

      No worries 😉

  25. Nantanut from BANGKOK

    Thank you so much you save me Thank thank you

  1. Lion in the Living Room « Glog

    […] Oh well, nothing the Googletron couldn’t take care of. […]

  2. Slow or Infinitely Long Shutdowns on Mac OS X » Boydo's Tech Talk

    […] Anyway, if the above hasn’t worked you can also try resetting the PRAM on your Mac by following these instructions. […]

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