Occasional problem of my computer not recognizing double keystrokes - ie the second 'l' in fall. Reboot solves

Have you tried looking under the "Accessibility Options" menu in the Control Panel? I'm thinking somehow the FilterKeys option is getting turned on, as the default shortcut automatically activates this feature if you hold the shift key down for eight or so seconds. Head on into the Control Panel and disable those shortcuts... see if that helps.