I have had trouble with a pi, basically high usb traffic can cause the ethernet controler to drop out. I have a 20 port usb 2 hub plugged into the pi, and it will run for a while then randomly the ethernet driver starts getting errors and drops out.

This is a known issue with the pi, something to do with voltage drops. In any event i ended up using a spare old pc and throwing centos on it. USB issues gone

Ive tried doing firmware updates on the pi, and there is a kernel boot option for the nic but these make no difference.