The reCaptcha example for ASP.NET does not seem to work. I followed the instructions but it always returns false, "The verification words are incorrect.".
The entries are good. I'm using localhost as the site but am not getting any public/private key errors which I did get when adding a bad key (as a test).
I've seen this error reported a lot but no good answers. Some suggest to call the validate on the control before checking to see if it is valid but this did not work for me.
I found another issue, it doesn't work under the Visual Studio web dev server but it does work under IIS.
It is possible to get this to work under web development server by launching the server as an external process. I have it on my tool menu. Change the server start to use "localhost" instead of launching web development. I looked at the source code and for the .NET control and it looks like here is already code to check for IPV6 name problems.
Hope this helps anyone who comes after me..