I can assure you that your bug is in konqueror or kaffeine, but not in the ffmpeg package. The error message you see come from the xine bundled ffmpeg copy, which has been compiled with xine's CFLAGS, which cause the stack misalignment. This does not seem to be a problem other this annoying warning, which I'm still investigating.
** Changed in: ffmpeg (Ubuntu) Status: Unconfirmed => Rejected -- "Libavcodec has been miscompiled and may be very slow or crash" (feisty) https://launchpad.net/bugs/83837 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs