recaptcha and createuser wizard

i do not get an error, but the create user wizard does not seem to work, as soon as i pluck the recpatcha off the page - the createuser wizard works as i would expect.
and vice versa

if i just have a recaptcha control on the page and no create user wizard the recaptcha behaves as expected.

if(Page.IsValid)

{
     CreateUser();
}
else

{
    return;
}

is really all that happens

i've also tried this

Recaptcha.RecaptchaControl mycaptcha = (Recaptcha.RecaptchaControl)CreateUserWizard1. ...