Thanks for the link - very useful. Have tried all 4 pins and only INT0 works, and on pin 3 as depicted in the graphic. INT1 on pin 2 does not seem to work at all (same for INT2/3) and I have found references elsewhere which indicate that this is an omission in the source code for the Leonardo, which implies it could be fixed. Unfortunately, cannot find out how to perform the fix and am not familiar with the lower-level stuff yet to know where to start.
I have make a fix for this. These attached files are for the IDE 1.0.1. I have pushed the Interrupts in the "right" order,
-Interrupt Number 0 works on Pin 0
-Interrupt Number 1 works on Pin 1
-Interrupt Number 2 works on Pin 2
-Interrupt Number 3 works on Pin 3
-Interrupt Number 4 works on Pin 7
For me it works.
Have fun with it.