JackCompiler version 2.5 hangs compiling the following class:
class Hang {
    function void hang(int a) {
        let a = a+1     // NOTE missing ;
        return;
    }
}
I'm running on Windows XP Home Edition Version 2002 SP 3
java -version reports:
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) Client VM (build 17.1-b03, mixed mode, sharing)
--Mark