I'm having a really strange issue with Yosemite GM Candidate 1 and my Mac Mini. I leave the Mini on 24/7 and just turn the monitor off when not in use. But if I leave it a few hours and come back to it the monitor gets no signal when I turn it back on. I click the mouse or press a button on the keyboard but it makes no difference the only fix is to turn the machine off and back on again. What makes the above more strange is I have already disabled the following: - Sleep - Monitor Sleep - Hard Drive Sleep - Screen Saver The only problems I have come across is a few permission errors: Code: Group differs on Library/Printers/InstalledPrinters.plist; should be 80; group is 0. Permissions differ on Library/Printers/InstalledPrinters.plist; should be -rw-rw-rw- ; they are -rw-r--r-- . User differs on private/var/db/displaypolicyd; should be 0; user is 244. Group differs on private/var/db/displaypolicyd; should be 0; group is 244. I am wondering if the displaypolicyd permission error could be the cause of my issues, but when I fix the error it re-appears after a restart Any ideas, fixes or suggestions? I don't really want to do another fresh install if I can help it. This problem never occurred on Mavericks either.