Mac mini display connection will not come back after sleep, I have to shut down and restart the monitor.

Finder icon on dock, macintosh hd, library, launch agent - delete all files & restart sleep to test

also

Finder icon on dock, macintosh hd,

Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist

delete file & restart sleep to test.

I'm not sure if this is exaactly the same issue so let me elaborate for my situation:

If I put my system to sleep, and it sleeps for some time greater than say 1-2 hrs, then when I go to wake it, the wake-up process starts, but my display (HDMI type) does not show the normal desktop - all is black - once saw a event notification upper right - however I do see the mouse cursur and can make it move on my screen. Seems to be some video corruption of sorts. No keystroke of any kind I tried do anything. I simply hold down power button for >5sec and cold boot again (ouch!) then back in operation ok.

I have a Mac mini with the same problem. The only way to get it to wake it up was with the volume keys. Soon after that I realized that if I change the sound to the internal speakers instead of HDMI the problem would disappear. The real problem for me was that if I wanted to use LogMeIn I needed someone home to hit the volume button to wake the computer. I change the sound output to use HDMI only when watching a movie or something. I always change it back to internal sound when done. That doesn't explain the cause of the problem (sorry), but, that's a work-around. I haven't had time, but, I have noticed that there are HDMI cables labeled with "Source" and "Display" on the ends. I am going to get one of these to see if it works.