MVC OAuth sign in with Google not working when using URL rewrite

Question

I use the standard OAuth functions that ship with MVC 4 to let users sign in with Google and Facebook. Everything was working fine until I used url rewrite to remove the virtual directory name from my godaddy hosted site (see http://support.godaddy.com/library/removing-virtual-application-name-from-urls/)

Facebook still works fine but google now fails every time. Google redirects back to the correct url but when the OAuth library tries to grab the information from the url it acts as if its not there.

I can't figure out why but I know it has something to do with the url rewriting as when I manually add the virtual directory name to the return url it works (but facebook breaks).

This is the code in web.config to remove the virtual directory:

<rule name="Remove Virtual Directory">
    <match url=".*" />
    <action type="Rewrite" url="{R:0}" />
</rule>

This is the OAuth code:

[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public ActionResult ExternalLogin(string provider, string returnUrl)
{
    var action = Url.Action("ExternalLoginCallback", new { ReturnUrl = returnUrl });
    return new ExternalLoginResult(provider, action);
}

//
// GET: /Account/ExternalLoginCallback

[AllowAnonymous]
public ActionResult ExternalLoginCallback(string returnUrl)
{
    var action = Url.Action("ExternalLoginCallback", new{ReturnUrl = returnUrl});
    AuthenticationResult result = OAuthWebSecurity.VerifyAuthentication(action);
    //AuthenticationResult result = OAuthWebSecurity.VerifyAuthentication();
    if (!result.IsSuccessful)
    {
        return RedirectToAction("ExternalLoginFailure");
    }

It all seems to fall apart here, even though the provider name is clearly visible in the url:

public static string GetProviderName(HttpContextBase context)
{
    return context.Request.QueryString[ProviderQueryStringName];
}

EDIT:

I have been able to get it working for now by changing the external login handler to this:

    [HttpPost]
    [AllowAnonymous]
    [ValidateAntiForgeryToken]
    public ActionResult ExternalLogin(string provider, string returnUrl)
    {
        var action = Url.Action("ExternalLoginCallback", new {ReturnUrl = returnUrl});
        var mustHackGodaddy = provider == "google";
        if (mustHackGodaddy){
            action = "/[virtual directory name]" + action;
        }
        return new ExternalLoginResult(provider, action);
    }

I wouldn't really call it a solution though. Can anyone shed some light on what is going on? I am wondering if the oauth library thinks it is an xss attack because of the re-written url. But it is strange that it only breaks for google and that the requests are also issued from the same url.