@dc42
I'm running into the same error msgs as h4t 
Basically just changing the signature in avrdude.conf makes no diff - same error msg.
Adding in new entrys in avrdude.conf and adding a new board just gives the
unknown MCU 'm328au' specified
(in my case its m328 as thats the name I tried to give mine)
This is a good game 
regards
Simon