Have been using my 7D for quite some time with ML without any serous hiccups, have lent it to coworker many times as well, no problems.
Now it seems to be frozen, it does not turn on at all,
*) tried all modes,
*) with card that was 100% working with ML,
*) formated on computer, on 40D, made sure that it is clean with eoscard, and even without card.
*) Tried other batteries, that I'm sure are ok, as worked on the same coworkers 5Dmk2, so batteries are ok
*) Took small battery out, left the camera off, on, with covers open and closed
and all combinations of above - camera seams to be dead.
only reaction I got was when instead of battery I attached it to external power adapter (that I use for long time-lapses), turned it on and it started to blink front yellow led with interval about 3 seconds...
FW 2.0.3, ML magiclantern-Nightly.2016Jul09.7D203
One think I could think off, it froze while using alternative battery, that sometimes had acted up, like on charger it is full, in camera show empty, but works like it had been full.