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Facing the exact issue. Archive and install did the trick, however, my iMac is pretty slow and messed up. Similar issues -- along with slowness -- have been popping up from time to time.

If you have a backup, do a clean reinstall of the Mac OS.
 
I do run time machine, so have a recent back up, but I'm in my final year of University at the moment, and got about 1 month left till graduating... So just in case I mess up and loose everything i'll wait for the last month and then try the re-install.

Thank you for your help :D
 
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