Calling a webservice from a webpart

[ALI-R]

Hi All,

I have a webservice on a win 2003 server and I'm trying to call it from
another win2003 server which is hosting my sharepoint portal server.

I am trying to call that webservice from a webpart but I get this error
which says :
System.Net.WebException: The request failed with HTTP status 401:
Unauthorized. at RSTreeWebPart.RSTree.reportsList() at
RSTreeWebPart.RSTree.RenderWebPart(HtmlTextWriter output)

If I put my webpart in the same server as the webservice resides everything
is fine.

Thanks for your help.

P.S. I'm using Intergrated Windows Authentication an in my web part I call
the webservice in this way:
ReportingService rService = new ReportingService(RSSever);
rService.Credentials = System.Net.CredentialCache.DefaultCredentials;
CatalogItem[] catalogItems;
catalogItems = rService.ListChildren(RepPath, true);