OS X Mountain Lion: Computer returns to the login window
After upgrading to OS X Mountain Lion, your Mac may keep returning to the login window after you have logged in.
You may have an incompatible startup item in your user account. You may need to start the computer in Safe Mode and disable login items by using the following steps:
- Shut down your computer.
- Wait 30 seconds
- Hold down the Shift key after pressing the power button.
- When you see the gray Apple logo and progress indicator (looks like a spinning gear), release the Shift key.
- If you are prompted to log in, type your password, then hold the Shift key again when you click Log in.
- Choose Apple () menu > System Preferences.
- Click Users & Groups.
- Click your account name, then click Login Items.
- Look for any application that has a prohibitory sign (a gray circle with a slash) over its icon. This indicates an incompatible item.
- Select the incompatible login item, then click the Delete (-) button.
- Restart your Mac.
If you receive an alert about any software being moved to a folder called "Incompatible Software" after upgrading to OS X Mountain Lion, please check with the software vendor to see if they have released a Mountain Lion-compatible version.