Listening to some (all?) mp3 streams on Fennec nightly builds seems to be broken. Attaching a remote debugger yields the message "Media resource (insert-some-URL-here) could not be decoded". Deleting all data and forcing a new profile doesn't resolve the issue. Neither does changing the plugin settings (enabled/disabled/tap-to-activate). This does not happen on desktop trunk builds (verified on Windows 7 and MacOSX). Firefox for Android 34.0b1 works fine, too. Not all mp3 streams have to be affected, but other formats may be as well. I'll try to narrow down the regression window.