I have my iMac password protected, so anytime it wakes from sleep or whenever the display sleeps, after waking it a login box pops up and I need to login before getting access. Every couple weeks, I'll wake the computer and no box will pop up. I'll see the mouse and can move it around, but the box is no where. In this case, I have to hold the off button on the computer to shut it down. It sucks, as I lose all my open windows. Is there any solution to this issue? Thanks!