June 2008 firmware.
If I start playing the movie with the IME on, the movie's regular audio is fully as loud as the IME. Pausing and unpausing causes the regular audio to go off and only the IME audio to stay on. I have not tried any other disks with IME and don't know whether this is a general problem or just the one movie.
I've also managed to pause it in the middle of the regular movie and get no sound; menu sound still works, and I'm wondering if it thinks the IME is on when it's not.
Also, with the IME on there are long stretches of just silence and no IME at all, which I'm not sure is a playback problem, or if the disk was just stupidly made with long stretches of silence.