Not able to Call a webservice from VISTA

We have a webservice deployed and calling it from Windows application, it is working for everbody except for 3 users who is using VISTA operating machine when they try to access the webservice from application they get the below error

"A Required prevelege is not h开发者_开发知识库eld by the client"

however they are able to access the webservice ASMX URL directly from browser with their credentials.

Can anyone tell me to figure out this issue

Try running the application as an administrative user and check it the problem persists.