Hi.

I also had a though time figure out a way to make this happen in firefox.
Code:
////////////////////////////////////////////////////////////////////////////////////////////// 
// firefox reports uncaught exception NS_ERROR_FAILURE with nsIXMLHttpRequest.send
// http://bytes.com/forum/thread681905.html
// http://radio.javaranch.com/pascarello/2006/02/07/1139345471027.html
// http://dev.rubyonrails.org/ticket/4267
...