Hello again BrokeCurmudgeon,
Thank you for responding to my post requesting additional information. As the keys work when you go back and retype them I doubt it is a hardware issue. I am leaning towards this being either a driver issue, software issue or operating system issue.
Thank being said we are going to try this one step a time starting with the easies the drivers. In the case of the drivers would like you to download and install the Original HP Multimedia Keyboard Driver which is the original driver that came with your computer for your keyboard.
Please let me know how this works for you. Thank you again for posting on the HP Forums. Have a great day!