Q: Recently, my mid2011 27" iMac began displaying flickering color squares on the monitor when accessing or activating graphics progr ... Recently, my mid2011 27" iMac began displaying flickering color squares on the monitor when accessing or activating graphics programs, i.e., CS6, Adobe Bridge or scrolling across the dock. Thoughts? more
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Helpful answers
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Dec 18, 2014 1:10 PM in response to COklineby Baby Boomer (USofA),★HelpfulIf you are still under warranty and/or have AppleCare, call them. Let them deal w/it.
OOW: Take your Mac to your local Apple Store or an AASP. Diagnostic testing is FREE!
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http://support.apple.com/kb/HT1379 Resetting your Mac's PRAM and NVRAM may help.
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Dec 18, 2014 3:53 PM in response to COklineby Old Toad,Is your graphic card a 6770 or a 6970? I ask because the 6970 had a recall and can be replaced for free is your are within 4 years of the purchase date of your iMac.
iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program - Apple Support
So check the model number of the graphic card carefully.
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Dec 22, 2014 2:13 PM in response to COklineby COkline,I appears that I have solved the problem. Apparently, the Mavericks update (done a few months ago) corrupted multiple disc permissions on my system. Using Disk Utility, I have corrected all permissions and the flickering color squares and other strange behavior seems to be corrected.

