It seems that some "abnormal situation" (нештатная ситуация) happened about a minute before Briz-M upper stage ignition, possibly during third stage separation of the International Launch Services' Centenario / Mexsat 1 mission, launched atop Proton M rocket, and the live webcast was cut about 10 minutes earlier than scheduled without expected report on the third stage separation and Briz M upper stage ignition.
For easier reference, since I likely got some of what I describe above wrong, here's the relevant part of Centenario mission's profile with timeline, ground track, and trajectory:
So far, not much else seems to be known about it, except what news Russian agencies hurried with minutes after webcast stopped, for example RIA Novosti or TASS. What I'm interested here is whether this launch anomaly has been confirmed, and if that's the case, what are its consequences. In particular, regarding potential orbital debris that such late deployment anomaly could cause.