Create a guest Account
and test if the problem still persists. To activate the guest account use the following steps:
- Open System Settings Users & Groups, click on the lock below to unlock it and type your password.
- On the left panel you see the Guest Account, activate it and log in and test.
- Deactivate it if you're done.
Repair disk permissions with disk utility
Sometimes files are corrupt and can be repair using the disk utility.
Try to reset the quicklook cache
Open Terminal (you find it in the utilities folder - see location above), and type the following commands:
qlmanage -r cache
After this is done you need to move some files to your desktop.
Open the following path location and move the files marked bold to your Desktop. Click on the Finder Desktop and press Command + Shift + G and insert the following path in the window:
Move the following files to your Desktop:
Restart and Test
Check for Hardware Issues
To see if there isn't a Hardware Problem restart your mac and press the D key during startup.