Mac OS X 10.6: If you can’t quit an application
If an application isn’t working and you can’t make it quit, you can force it to quit.
Important:When you force an application to quit, you lose any unsaved changes to documents that are open in the application.
Here are ways to force an application to quit:
Choose Apple menu > Force Quit, select the application in the list, and click Force Quit.
Hold down the Command and Option keys and press Esc. Then select the application in the list and click Force Quit.
Hold down the Option key and press the application’s icon in the Dock.
After you force an application to quit, try using it again. If it still doesn’t work, try restarting your computer.
If you continue to have problems, you may need to install the application again or contact the application’s manufacturer for more help.