|The problem began after I installed some microsoft update relating to languages. If either of your scenarios were correct then I would not be able to type an uppercase "L" after the lowercase "l" disappears.|
However, when the screw-up occurs, I can switch to the Dvorak keyboard and everything is correct except nothing appears when I hit the "p" key, but when I hit "P" (shift-p) I see "L." When I hit the "l" key I see a lowercase "n" as expected. This says both the motherboard and keyboard are functioning correctly. It's another Microsoft screwup.
There have been many posts about this problem on the internet. The only solutions that eventually work are rebooting, rebooting, rebooting... and switching to another keyboard layout and then back to US English.