OK. That was it. After removing FTDI* (Wacom and FTDI supplied), things just work for Duemilanove board. And my Wacom tablet isn't complaining either. If I had to guess, Wacom driver probably suppressed generic Apple provided driver (and FTDI provided one), and caused things to not work.
antaljani: Do you have any additional hardware (and drivers installed) that may cause conflicts; e.g. similar to the problem I had? Wacom tablets? Anything else?