Don't make the user press the Back button.
Re-present the data from the previous screen on the current one, with
a new reCAPTCHA.
Not only does this 'fix' your reCAPTCHA problem, it also solves the
terrible UI problem of having to 'press back.'
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PJH
http://shabbleland.myminicity.com/
http://www.chavgangs.com/register.php?referer=9375
http://www.kongregate.com/?referrer=Shabble