Just made the upgrade to Yosemite but now my iMac wont restart or shut down. Whenever I try to do any of these it stays on a black screen with a mouse pointer, and I have to turn it off and back on manually.
Mine was showing a black screen after I updated my iMac to Yosemite.
I unplugged my USB mouse and the new Login screen was displayed.
No restart was necessary.
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