“Switch to Safe Launch

The Quit Unexpectedly dialog box gives you the option of reopening an application that has just crashed. But if the application quits on you a second time, Tiger now gives you a new option: Try Again. When you click on this option, Tiger opens the program in Safe Launch mode, which prevents the application from accessing its preferences file. Corrupted preferences files are a common cause of application crashes.

If the Safe Launch mode is successful, you’ll have to make a decision. When you quit the application, Tiger will ask whether you want to preserve the new settings. In most cases, you’ll want to click on Yes. When you do, Tiger renames the original (presumably corrupt) preferences file by adding a .saved extension to its name. The application ignores the old file on future launches. However, this means that you’ll have to re-create any changes made to the old preferences file.”

http://www.macworld.com/2005/09/features/tigertips6/index1.php