My Avalon3 is hashing away just fine. (needed to raise the voltage some to reduce the error rate to under .5%).
I compiled Cgminer from source with --enable-avalon2 flag.
Then added -S /dev/ttyUSB0 --avalon2-voltage 7250 --avalon2-freq 500 in addition to my normal configuration to the command line.

If you are feeling adventurous the avalon-usb branch of cgminer in BitSyncom's git has some nice updates.