I was receiving the same error with my Duemilanove ATMEGA328 on OSX. The problem was resolved by updating my FTDI drivers from here: http://www.ftdichip.com/Drivers/VCP.htm
I was receiving the same error with my Duemilanove ATMEGA328 on OSX. The problem was resolved by updating my FTDI drivers from here: http://www.ftdichip.com/Drivers/VCP.htm