This may be a slightly off-the-wall suggestion, but ...
Are you comfortable compiling C?
Tod E Kurt has a little program to open a serial connection (over USB) to an Arduino at
http://todbot.com/blog/2006/12/06/arduino-serial-c-code-to-talk-to-arduino/
If you can, download, compile and run it, you should see the Tx and Rx LEDs flash if you run the program, and find the name of the correct /dev/ to connect to the Arduino.
If there is a /dev/ name that looks correct, and this program flashes the Tx/Rx LEDs, then the drivers are likely to be correct.
Just a thought.
HTH
GB