colinramsay.co.uk

It seems that XMLHttpRequest.readyState == 2 doesn't just refer to requests which work. State 2 is supposed to occur after send() has been called and the header is available. However, if a timeout occurs, that's still state 2 - even though the site headers aren't available. So what that give us is a good way of trapping timeout errors:

httpReadyStateChange: function(){
  if(Update.httpReq.readyState == 2){
    try{
      Update.httpReq.status;
    }catch(e){
      Update.httpReq.abort();
      Update.gochangeit(-10000);
      return;
    }
  }
}