Hello all, I am having an issue with my 2013 iMac 27" in which the system works fine for a few days, but intermittently decides to freeze when I try to wake it up from sleep. The system is using an external SSD in a thunderbolt enclosure as the boot drive. It has been on this setup since I purchased it new in mid 2014. However ... recently, it started giving me this problem: When I try to move the mouse or hit a key on the keyboard to wake the machine, it simply shows a black screen. The login screen never appears, and I am forced to hold the power button and reset manually. This freezing when I try to wake seems to happen when I leave the machine alone (in sleep mode) for more than 24 hours. Is anyone else having this issue? Is there a fix? I have already tried resetting the VRAM, SMC, etc.