soapUI authentication problem

I'm using soapUI 2.5.1 and am trying to pass credentials from one domain to another domain that has SPNEGO security.  I just can't seem to get past the security wall.  I'm passing username, password and domain via the request properties box and I get back the generic SPNEGO..."Error 401: Message from SPNEGO TAI: Your browser configuration is correct, but you have not logged into a supported Windows Domain. Please login to the application from a supported Windows Domain."

I'm brand new to soapUI and web services.  I've run successful tests across common domains, but this one is annoying.  Can anybody point me in the right direction?