Launch the Open Firmware Password Application.

Click the authentication icon and enter your Administrator credentials. You will be prompted for a password.
Locate and click the Change button.

This will launch an Open Firmware Password window.

In the Open Firmware Password window, locate and click to deselect/uncheck the “Require password to change Open Firmware settings” option.

Click the OK button to commit your changes.

Locate and re-select the lock icon.

How to Disable Mac OSx Firmware Password Protection