Start your Mac in Safe Mode:
To start up into Safe Mode (to Safe Boot), do this:
- Be sure your Mac is shut down.
- Press the power button.
- Immediately after you hear the startup tone, hold the Shift key. The Shift key should be held as soon as possible after the startup tone, but not before the tone.
- Release the Shift key when you see the gray Apple icon and the progress indicator (looks like a spinning gear).
During startup in Mac OS X v10.4 through Mac OS X v10.6.8, you will see "Safe Boot" on the login window, which appears even if you normally log in automatically. During startup in Mac OS X v10.2 through v10.3.9, you will see "Safe Boot" on the Mac OS X startup screen.
To leave Safe Mode, restart the computer normally, without holding any keys during startup.
Read about it: Mac OS X: What is Safe Boot, Safe Mode?
Safe Mode or "Safe Boot" is a troubleshooting mode that bypasses all third party system extensions and loads only required system components. Starting in Safe Mode will take much longer than usual and some features (such as iTunes) do not work in Safe Mode. This is expected, and your usual work environment will return after restarting normally.
Does the problem still exist while in Safe Mode?