vb.net – Office加载项安装VSTO下载失败

>下载并执行setup.exe
>验证所有先决条件(.Net框架等)
>已下载vsto文件

到目前为止,安装此加载项的每个人都没有遇到任何问题(此加载项已使用了大约一年).我们有一个新客户在Windows 7上安装它,我们正在看第一期.这是错误：

There was an error during installation:
Downloading http://<path and filename>.vsto did not succeed

***************** Exception Text******************
System.Deployment.Application.DeploymentDownloadException: Downloading http://<path and filename>.vsto did not succeed
System.Net.WebException: The remote server returned an error: (407) Proxy Authentication Required. ---> System.ComponentModel.Win32Exception: The token supplied to the function is invalid
at System.Net.NTAuthentication.GetOutgoingBlob(Byte[] incomingBlob,Boolean throwOnError,SecurityStatus& statusCode)
at System.Net.NTAuthentication.GetOutgoingBlob(String incomingBlob)
at System.Net.NtlmClient.DoAuthenticate(String challenge,WebRequest webRequest,ICredentials credentials,Boolean preAuthenticate)
at System.Net.NtlmClient.Authenticate(String challenge,WebRequest webrequest,ICredentials credentials)
at System.Net.AuthenticationManager.Authenticate(String challenge,WebRequest request,ICredentials credentials)
at System.Net.AuthenticationState.AttemptAuthenticate(HttpWebRequest httpWebRequest,ICredentials authInfo)
at System.Net.HttpWebRequest.CheckResubmitForAuth()
at System.Net.HttpWebRequest.CheckSubmit(Exception& e)
--- End of inner exception stack trace ---
at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.InstallAddIn()

显然,我不能从我的位置复制.我的直觉告诉我这个客户的网络安全问题导致了一个问题(我的理解是他们有一系列防火墙等),但他们的Windows XP机器安装没有问题.

有人看到我遗失的任何东西吗？