JRBarrett: Can't swear on a 777 but on a NG737 all four flight recorder box breakers are in the cockpit (it gets power from both ac buses and both dc buses. CVR is in the cockpit as well. On the ACARS MU it has 2 breakers one on an ac buss and one on a dc buss. both on the flight deck as well.
It does seem like either the ACARS MU died at the worst possible time, or someone pulled the breakers.