Thanks, you two – I really appreciate the feedback and help! I had previously tried adding that to the CSS for the skin and thought it broke the skin. However, retesting just now, I discovered it was a PBCAK, as I had not switched the player controller before previewing. D’oh!
I tried using Inspect Element in IE and Firefox as well as using NVDA to see what it read to see if I could figure out what element is “breaking” tab functionality for the CC button in IE. No luck yet.
Out of curiosity, can I add the pseudo class :focus to the buttons? I know the :hover works, so my inclination is to believe that :focus should work similarly. If I can do it in the skin, that adds a layer of accessibility to the player by creating a larger focus area for tab users.