iMac won't restart after upgrade to Yosemite 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.

Any help?
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.