When prompted for a Captcha by SU, There's no visible captcha text and no input box. The only thing visible is the "I'm a human" button.
Windows XP, FireFox 4
Form Source:
<form method="post" action="/captcha?s=47e22f3a-3f5c-4c8c-8df9-c9b24b7b19e5">
<div><script type="text/javascript">
var RecaptchaOptions = {
theme : 'clean',
tabindex : 0
};
</script><script type="text/javascript" src="http://api.recaptcha.net/challenge?k=6LcDNwYAAAAAAG_X1rC8kTtLBP6XS2Ym1N0n9kSY">
</script><noscript>
<iframe src="http://api.recaptcha.net/noscript?k=6LcDNwYAAAAAAG_X1rC8kTtLBP6XS2Ym1N0n9kSY" width="500" height="300" frameborder="0">
</iframe><br>
</br><textarea name="recaptcha_challenge_field" rows="3" cols="40"></textarea><input name="recaptcha_response_field" value="manual_challenge" type="hidden" />
</noscript></div>
<script type="text/javascript">
$(function() { $("#recaptcha_response_field").focus(); });
</script>
<noscript>
You must enter the confirmation code in the box above after solving the challenge
</noscript>
<p>
</p>
<input id="btn-captcha" style="font-weight: bold;" type="submit" name="post" value=" I'm a Human Being " /><br>
</form>