If the PRAM reset doesn't fix it, it sounds like a bad 10.8 update or a hardware issue.
Try to see if you can do a #8 here
Make sure to reboot twice so EFI takes hold as that loads first before OS X .
You can install OS X on a external drive and boot from it, see if it's not a hardware problem.
Hey Apple Community :)
I have an iMac (mid-2011, i5, 16 GB RAM, 500 GB HDD...) that is getting the same "grey splotches" during initial boot. At first I thought it was the hardware, but at one point I had the HDD partitioned (10.6 and 10.8) and thought it could have been the culprit... Here is why:
When booting to 10.6...no issues.
When booting to 10.8...distortion.
I have removed the partition, reinstalled 10.6 and completed the upgrade steps via the App Store to get back to 10.8 (thinking a fresh reinstall might fix the issue)...same problem occurs when booting into 10.8.
Short of contacting Apple Care, does anyone have any suggestions other than what is listed in this thread?
Thank you in advance for your consideration!
I just bought a used 2011 17" Macbook Pro and and having similar annomolys on the start up screen. They only appear after putting in the password when the screen goes white before the desktop appears. Has anyone figred out what is causing this and if it is a serious problem or not ? Resetng the PRAM did not fix the problem.