I have spent many days searching for an answer to this issue. I have Processing 1.5 and Ardino 1.0 on Ubuntu 10.04. Arduino IDE can talk to hardware but Processing can't, I initially had the RXTX version mismatch issue, but that no longer errors since I downloaded the RXTX Pre1 and placed it in the Processing folder as instructed elsewhere. That error is now gone, but now doing a simple Serial.list() gives an ClassNotFoundException: gnu.io.SerialPortEventListener error (after a lomg pause). String portName = Serial.list()[0]; gives the same error.

At this stage after not finding one full set of remedy steps, and after teasing out parts from various solutions, I think my Serial/RXTX components are probably messed up. I'm thinking I need to start over with a reinstall of Processing and Arduino and  start afresh. I've not had any of these isseus in Windows and my project which is supposed to run in Ubuntu is now two weeks behind. I'm getting close to kicking Ubuntu and making this a Windows solution. I really don't want to do that so I'm hoping someone out there has gotten Ubuntu 10.04 (or I'll take whichever version works) to work with their Arduino and Processing and will share their step-by-step solution.

Any and all suggestions are most welcome.

Thanks in advance