Since your using a RPi try to stay clear of raspberian. It has a wonky install of libusb that has been causing problems. Arch Linux has been verified as working.
I experienced issues with Block Erupter USB's on Raspbain. However I was successful at building and running cgminer from git (3.3.1) after dist-upgrading Raspbain from wheesy to jessie. Rock solid now and hot plugging works flawless. Thought you should know. Sorry for straying off topic Canary
