iMac not responding on black screen
Can somebody help me with the problem that after my iMac has been on all night and when i try to work on it the next the day it stays on a black screen and cannot get it out of the black screen mode anymore (no mouse cursor shown). I can hear the iMac is still on. iMac doesn't respond on mouse or keyboard clicks and only shutting iMac off by holding power button to shut it down and start it again by hitting power button helps.
Under here the details of my iMac:
iMac (27-inch)
3,2 GHz Intel Core I5
8 GB 1600 MHz DDR3
C0*****8J4
What i already tried is:
- Deactivated screensaver
- Option to turn on hibernation after screen is turned off (after 45 min)
<Personal Information Edited by Host>
iMac, OS X Yosemite (10.10.1), null