Of course now that you have both pointed this out, it makes complete and utter sense. All I can say is that it was late .... and I was tired
Having said that, I did take another look at the leJOS README.html file and have to say that it isn't entirely obvious from first reading that the NXT firmware *must* be replaced in order to use leJOS.
Maybe you might consider a small note to this effect in the "Using LEJOS NXJ" section?
In any case, thank you for your help!