I am attempting to get a basic ECMAScript parser working, and found a complete ANTLR grammar for ECMAScript 3, which appears to compile ok and produces the appropriate Lexer/Parser/Walker Java files.
(Running inside ANTLR IDE plugin for Eclipse 3.5)

However, when actually trying to use it with some simple test code (following guide on ANTLR wiki), it just hangs when trying to create the parser:

CharStream MyChars = new ANTLRFileStream(FileName); // FileName is valid
ES3Lexer MyLexer = new ES3Lexer(MyChars);
CommonTokenStream MyTokens = new CommonTokenStream(MyLexer);
MyTokens.setTokenSource(MyLexer);
ES3Parser MyParser = new ES3Parser( MyTokens ); // hangs here
ES3Parser.program_return MyReturn = MyParser.program();

I've tracked down the problem to inside the ES3Parser constructor, where it's calling the function proxy.handshake() - before this line I can successfully do System.out.println("text") but after it I get nothing.

So, how do I go about finding out why it's hanging, and stopping it - or even just bypassing this section (can/should I disable debugging?) - so long as that lets it work and allows me to get on with doing useful stuff.