Hi,
I use Arduino Boards as Interface for max msp. up to the board Arduino Duemilanove (both ATmega 328 and ATmega 168) PDUINO for Max and Maxuino worked fine. With Arduino UNO they refuse however. I am easily able to upload "blink" and other stuff to Arduino UNO out of Arduino's API and it works. As soon as I change to max msp (after uploading the correct Firmata stuff) the communication doesn't function properly. It must have something to do with the new communication over the AtMega 8U2 programmed as a USB to Serial converter. Also in Max it shows "usbmodem1d11" nothing like /dev/tty.usbmodem1d11.
Has anyone out there found the solution to this new problem?
Thanx for Help.
I had a similar problem - I'm using the OneWire library and this wouldn't run on Uno - I updated the FTDI firmware following these instructions and now everything is working 
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1286088093/30/#34
Uploading with Arduino 22 solved the problem. Apparantly Version 20 and 21 (with which I tried) had a bug.
Thank you for your support