I am always RAS'd into MS CorpNet VPN under my REDMOND account.

I am always able to ping "itgproxy.redmond.corp.microsoft.com"

I instantiate a System.Net.WebProxy object as follows:

using System.Net;
string proxyUrl = http://itgproxy.redmond.corp.microsoft.com;
WebProxy proxy = new WebProxy(proxyUrl, true);
MSNSearchService.Proxy = proxy;

I make a web method call to MSNSearchService.Search()

During certain periods of time, this calls always successfully returns
expected result data.  During other periods of time, this call always
times-out.

When I'm experiencing the time-outs, purely due to frustration, I've
unsuccessfully tried the following variations on the proxy url :

string proxyUrl = "http://www.itgproxy.redmond.corp.microsoft.com:80;"
string proxyUrl = "http://www.itgproxy.redmond.corp.microsoft.com;"
string proxyUrl = "itgproxy.redmond.corp.microsoft.com;"

All fail.

All of my other code for configuring and calling my web method remains
constant.  The proxy url string is the only code I ever change.