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

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