CasperJs not capturing screenshot for some sites - extjs

Question

I have written some test case using CasperJS.
var baseUrl = "http://cng20018241:9090";
var require = patchRequire(require);
casper.options.viewportSize = {
width: 1024,
height: 800
}
casper.test.begin('Connecting to site', function suite(test) {
casper.start(baseUrl, function() {
this.wait(5000, function() {
this.echo("I've waited for 5 seconds.");
});
})
.then(function(){
this.captureSelector('c:\\temp\\screenshot.png', 'html')}
)
.run(function() {
casper.echo("TESTS COMPLETED", "GREEN_BAR");
casper.exit();
});
});
var partial = function(func /*, 0..n args */) {
var args = Array.prototype.slice.call(arguments, 1);
return function() {
var allArguments = args.concat(Array.prototype.slice.call(arguments));
return func.apply(this, allArguments);
};
};
The above code is capturing the screen shot for a site developed using meteor. But if I change the url to a site developed using ExtJs, casperjs only produce screenshot which is black. it does not capture the actual screen.
Both the sites are internal sites. The site developed using ExtJs (not working) uses windows authentication.
What options do I have now?
After registering various events, I am getting following error:
ResourceError: {
"errorCode": 5,
"errorString": "Operation canceled",
"id": 0,
"url": "http://cng20018241:9090/"
}