Adding a remote Web Reference and 'Discovery Credential' – Issue

Hi

I have developed an asp.net web service and deployed it Win 2003 server on IIS 6. I tried to access it from my asp.net application which is in developer pc, i'm getting a
dialog-box "Discovery Credential for Proxy Server"... which asks for a user
and password.

Even when I provided right credentials it is not accepting. May be this is because of firewall. How can I get rid of this.

Please help asap.

Thanks