I have a client who is stuck!!!

In my VB6 application I am making a call to a web service. One client using our application in the production environment is reporting that his machine locks up when performing the web service call. No other clients hitting the same web service are having problems.

Does anyone have any idea as to what would make the XMLHTTP.Send method hang?

Clients's machine Specs.
OP = Windows XP Service Pack 2
MSXML 3 and 4 have been installed
User can access the HTTP call manually through his browser.

Code is as follows

Dim xmlURL As XMLHTTP

Set xmlURL = New XMLHTTP

xmlURL.Open "POST", "http://WebServiceAddress", False, UserName, Password
xmlURL.setRequestHeader "Content-Type", "application/xml; charset=utf-8"
xmlURL.Send "xml Text"

Thanks for your help!