Have you confirmed that the rate in the Processing serial connection matches that in your Arduino sketch?  That would be the first thing I'd check.  Depending on the Arduino code you may also need to send a byte from Processing in order for a message to be sent, though in this case you'd also need to do this when you connect to the serial port from the Arduino interface, so it doesn't sound like that's the problem.

After that things get a little more tricky.  Are you using println to display received messages in the Processing output window?  You obviously need to confirm what, if anything, is getting through and this should help confirm that...  If something is getting through, and it is intelligible, then I'd guess the parsing routine in Processing needs fixing.

Not sure how much any of that helps - must admit I'm fairly new to Arduino and have only run a couple of tests with it and Processing...

Well I guess you now need to make sure the data coming through from the Arduino matches what the Processing code 'expects':  println() the serial data to see what you're getting, then check the parsing routine in Processing and make sure it's getting the data format that it needs in order to feed the data into the graph.  I'd guess you're assigning the values to variables so you could println each of these too - maybe some of them are working and others not; so that should help identify the culprit.

BTW I just noticed there's a forum dedicated to this kind of question.  It may be worth posting follow-up questions here, then your question will be seen by the best people to give you an answer