This article describes why Firefox may close itself unexpectedly when using Yahoo!® Mail. For problems with Firefox crashing when not using Yahoo!® Mail, see Firefox crashes

Yahoo!® Messenger

The Yahoo!® Application State plugin can cause crashes. You'll need to disable this plugin.

1. At the top of the Firefox window, click on the Firefox button (File menu in Windows XP) and then click ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select QuitAt the top of the Firefox window, click on the File menu and select ExitOn the menu bar, click on the Firefox menu and select Quit FirefoxAt the top of the Firefox window, click on the File menu and select Quit.
2. Open My Computer or Windows Explorer.
3. Browse to the directory: C:\Program Files\Yahoo!\shared
4. Delete the file npYState.dll. Now that this plugin has been removed, Firefox may stop crashing when using Yahoo!® Mail.

Removing the plugin will not affect your ability to use Yahoo! Mail.