After upgrading to yosemit login screen freeze upon waking up

Question

After upgrade to Yosemite, my MacBook Air (1.3 GHz Intel Core i5, 8GB 1600 MHz DDR3, Intel HD Graphics 5000 1536 MB)  sometimes freeze upon waking up, at login screen. With a white Apple logo on the top left corner of the screen, my login user name in the center, Cancel button at the bottom of the screen, and the usual login password text box is not available. I don't have control of the mouse or keyboard. This usually happens after extended sleep.  The only way out of this situation is to hold down the power button to restart.
The only application I'm running at the time of sleep (closing the lid of my macbook air) is Parallel 9, with Windows 7 and Microsoft Outlook running inside the virtual machine.  After rebooting the system, and relaunching Parallel, Windows 7 reports that it was shutdown unexpectedly.
Has any one run into this? Will upgrading Parallel 10 fix this problem?

Answer 1

I haven't found or seen a permanent solution. A temporary solution from another user is to change the screen resolution to the next lower. It solves the problem for now, at least for him. One other disbled their screen saver and increased the time period before sleep mode kicks in. Otherwise, the obvious is to disabled the sleep mode entirely for the time being. These are from people with different hardware. These may or may not help. If I run across a real fix I'll let you know. Appreciate, if you can do the same.