I am having an issue with .NET detecting the proxy settings configured through internet explorer.

I'm writing a client application that supports proxies, and to test I set up an array of 9 squid servers to support various authentication methods for HTTP and HTTPs. I have a script that updates IE to whichever configuration I choose (which proxy, detection via "Auto", PAC, or hardcode).

I have tried the 3 methods below to detect the IE configuration through .NET. On occassion I notice that .NET picks up the wrong set of proxy servers. IE has the correct settings, and if I browse the web with IE, I can see I am hitting the correct servers via wireshark.

WebRequest.GetSystemWebProxy().GetProxy(destination);

GlobalProxySelection.Select.GetProxy(destination);

WebRequest.DefaultWebProxy

Here are the following tips I have:

• My script sets a PAC file on a webserver, and updates the configuration in IE, then clears IE's cache
• .NET seems to get "stuck" on a certain proxy configuration, and I have to set another configuration for .NET to realize there was a change. Occasionally it seems to pick some random set of servers (I'm sure they're not random, just a set of servers I used once and are in some cached PAC file or something). As in, I will check the proxy for the destination "https://www.secure.com" and I may have IE configured for and thus expect to get "http://squidserver:18" and instead it will return "http://squidserver:28" (port 18 runs NTLM, 28 runs without authentication). All the squid servers work.
• This does not appear to be an issue on XP, only Vista, 2003, and windows 7.
• Hardcoding the proxy servers in IE ALWAYS works
• Time always solves the issue - if I leave the computer for about 20 or 30 minutes and come back, .NET picks up the correct proxy settings, as if a cached PAC script expired.