Per my post two up (#630) my setup for a single U3 has been perfectly stable for like a week.  I've been running it slightly overclocked, 775v and 237.5freq and it's been performing like a champ at about 58-60gh.

I bought two more U3s, however, I cannot get more than one of my 3 to run at the same time (I have so far only tried to get 2 going at the same time).  I'm using cgminer 4.9.0 (4.9.1 won't see a U3 on my computer for some reason) with stock volt and freq while I try to get more than one going concurrently.  I've tried launching cgminer with 2 plugged in at the same time and I get constant LIBUSB from both devices.  If I unplug one the other runs just fine.  If I launch cgminer with just one running it hums along perfectly, then I'll hotplug the second one in and instantly the LIBUSB errors start.  I've tried with them both plugged into my powered USB 2.0 hub, and tried with one in the hub and the other in a separate USB port on my computer, but same results.

Is there something special that needs to be done to get multiple units running at the same time?  Any of the three work by themselves.  Thanks for suggestions.