I compiled the rxtx library v2.2pre3 myself (current cvs head, check  http://www.neophob.com/2010/07/serial-library-rxtx-v2-2pre3/ if you want to download it). for mac osx the maximal serial speed is 230400 - but i'm unable to connect my arduino at that speed. 

Hi michueo,

I am on a PC with this serial device that runs on 1250000.... I set the serial up in my processing sketch like this:

myPort = new Serial(this, portName, 1250000, 'E', 8, 1);

sent the byte sequence command, nothing happened... so I used a serial monitor program and realized the baud rate was 9600 the whole time... Then I bumped into your post and realized this might be a maximal speed issue. I changed the speed to 115200 it showed up in the monitor correctly. I also tested a few other non-standard numbers and saw 9600 too. So far I realized that there is a maximal number, and the number has to be one of the standard baud rate numbers.

best,