For an educational program I use a webservice for acces to a central database
on a remote server. The webservice is is being accessed over https. So far
this worked fine on the computersystems in the about 20 schools that are
participating.
On one school however, a problem occurs since they changed from internet
provider.
The problem seems to be to get the response back from the webservice. This
is the error message:
System.Net.WebException: Underlying connection closed: can't make connettion
with remote server
  at System.Net.HttpWebRequest.CheckFinalStatus()
  at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult)
  at System.Net.HttpWebRequest.GetResponse()
  at System.Net.Connection.TunnelThroughProxy(Uri proxy, HttpWebRequest
originalRequest, Socket& socket).

I don't call the HttpWebRequest methods directly from my code, they are
called from within the webserviceproxyclass that I generated with wsdl.exe.

The problem only occurs when the user doesn't have administrational rights.
When the adminstrator himself logs in on the computer, calling the webservice
works fine, like before.

I have no clue yet where to look for the solution. Any suggestions would be
very welcome.

Additional information about the schools LAN (from where the program is
executed): server had windows 2000, clientcomputer has windows XP.
Internetconnection over asdl, no proxyserver used.

Jan