well... i do not really know if it's an anti-hack or some new hot stuff.
following happend to me:

i used exploit, mh, drophack, dropbnet, kloader.
everything went fine as always but suddenly i joined a rt game, where me and another hacking ally could not see our peons. after the other 2 mates left we couldn't even control their units, which means: no drop, no build exploit!

if it's some kind of antihack, big congraz to the guy who made it.
pretty nice idea... but if its just another hack... screw you ;]

anyone else already faced that shit?