Windows remembers the keyboard layout setting per application and you may have changed the keyboard layout by accident via a keyboard shortcut. See: * http://support.microsoft.com/kb/306993 - HOW TO: Use the Language Bar in Windows XP ---- It is possible that you have switched the keyboard layout by accident. * Make sure that you have the Language bar visible on the Windows Taskbar. * You can do that via the right-click context menu of the Taskbar: Toolbars > Language Bar. * Check the keyboard language (keyboard layout) setting for the application that has focus via the icon on the Language bar. * You need to do that while Firefox has focus because Windows remembers the keyboard layout setting per application. * The default keys to rotate the layout is a combination (Ctrl+Shift or Alt+Shift) that can easily be used in Firefox to activate a menu item. * To avoid an unintentional switch, assign a specific key sequence (Alt/Ctrl+Shift+number) to select keyboard layouts and remove the key combination to rotate layouts (Alt+Shift or Ctrl+Shift)