I have a simple key/value list in JSON being sent back to ASP.NET via POST. Example:
{ \"key1\": \"value1\", \"key2\": \"value2\"}
Mark Rendle posted this as a comment, I wanted to post it as an answer since it's the only solution that has worked so far to return the success and the error-codes json results from the Google reCaptcha response.
string jsonReponseString= wClient.DownloadString(requestUrl);
IDictionary dict = new JavaScriptSerializer().DeserializeObject(jsonReponseString) as IDictionary;
Thanks again, Mark!