I'm trying to get 80 Gridseeds working across 4 Raspberry Pi's (24 Gridseeds for each Raspberry Pi using Monoprice 24-port USB hubs). However, I'm running into an issue with btbartle's cgminer:

http://i.imgur.com/wbdUUuA.png

It looks like the Gridseeds are hashing, but only 3 of them have submitted shares, and a very low amount at that (and strangely, it always increments by a power of 2). Does anybody have any idea why this is happening? I've tried using the default 600 MHz speed and also using cpuminer, but the results are always the same.