I can't seem to limit my Antminer U1's speed any more.
It looks like the always goes to 2.1 GHh/s, no matter if I start them with 0781 or any other value. Then they overheat, and gets reconnected.

Any idea what can be wrong here ? I have 6 devices connected to a 10 port hub, powered by a 5V, 4A PSU brick. Even if I disable 2 of them in bfgminer I have the same problem.