While improving my Blog i recognized a problem with the often used WP Audio Player. Audio Player is a Plugin to WordPress that uses a simple HTML5 – Flash Fallback solution to integrating audio into your blog. I used it since a few weeks, yesterday it stoped working – but only in Firefox. According to a short google search this issue is quite common.
In case this happens again, or happens to anyone else, i try to exactly describe the issue and the way i got rid of it.