Install freezes
I was upgrading 2 iMac (2013) and one MacBook Pro (2010). All was well on one iMac and the MacBook Pro. On the second (same model, same purchase date) iMac, the screen is frozen on the second reboot screen at about 50%. Some reports say just wait; some say do a forced shut down and reboot. Help needed please.
iMac (21.5-inch, Late 2013), OS X Yosemite (10.10.1), upgrading from Mavericks