URL monitoring problem

Hi There,
I have a url that require a Basic Authentication. While setting up the monitor, If I am not included the username and password. I got this error message

The request requires user authentication. The response MUST include a WWW-Authenticate header field (section 14.47) containing a challenge applicable to the requested resource. The client MAY repeat the request with a suitable Authorization header fi

But if I do provided the username and password, I got different error message as follow

Some other error occurred in contacting the server, making the request, or parsing the response. This could be due to a mangled or incorrectly formatted response from the server

Please help how to make this works.
Thanks,
Robert