Mono: HttpWebRequest SSL Errors on non-SSL URI

Question

I have a console application that I wrote for .NET/Windows that I suddenly had the need for on my unix system. Mono has, for the most part, been hugely successful at providing this for me.

There is however a small issue - The application issues many HttpWebRequests as it runs, and for a small portion of these, Mono is returning an error:

 Error getting response stream (Write: The authentication or decryption has failed.): SendFailure

This error message seems to indicate an SSL error. However, this application does not issue any request to SSL-secured URIs (i.e. all URIs are http://).

The main code in question is as follows:

HttpWebRequest req = WebRequest.Create(url) as HttpWebRequest;
req.UserAgent = UserAgent;
req.AuthenticationLevel = AuthenticationLevel.None;
req.AllowAutoRedirect = true;
req.KeepAlive = true;
req.CachePolicy = new RequestCachePolicy(RequestCacheLevel.NoCacheNoStore);
req.Timeout = timeout;

if (useCompression) {
    req.Headers.Add(HttpRequestHeader.AcceptEncoding, "gzip,deflate");
}

EDIT: For the purposes of running this code, you can define dummy variables as follows:

string url = "http://www.google.com";
string UserAgent = "WhateverBot";
int timeout = 5000;
bool useCompression = true;

It should be noted that the code works without any problem on Windows/.NET.