Accessibility issue: Audio-CAPTCHA fails with keyboard navigation

I recently found out that it's impossible to play the audio captcha when navigating by keyboard only. It's just not possible to focus on the play button. Same is true for leaving the audio player once you got there by using a mouse. It's not possible to tab in or out by keyboard. Has anybody been aware of that yet? Couldn't find an issue here.

It's probably some problem with the flash plugin, I guess. But the audio CAPTCHA of reCAPTCHA is perfectly navigable by keyboard only. Maybe they got a solution that might work on Mollom, too?

Regards,
daniel / klickreflex