I have a late 2012 27" iMac, running Yosemite. I downloaded El Capitan from the App Store. It took about 25 minutes or so to download. It then produced an error, An error has occurred. I have since: Rebooted Checked for unfinished downloads Manually cleared out the App Store cache, then redownloaded. Applied Safari 9.0 update with Update All button Nothing works. I cannot get any more information about the error that has occurred. Any ideas?