Well after reading over the thread on USB Hubs, and doing my own math, I realized that even though it was a 7 port hub that I was using, the powersuply would only support 6 per hub.  I went through my setup and removed one from each hub, so that I'm only running 6 in each now.  That did the trick!  Now I have 52 of them running perfectly for a combined hash rate of 17Gh/s.