[Plugin: Contact Form 7] Second form Submit button issue with Acceptance

I am having an issue with creating a contact form with Acceptance checkbox. Essentially the submit button creates an extra attribute in it, which means the Submit button does not work in FireFox, Chrome and Safari. Without the checkbox, the form submit button code looks like this:

<p><input type="submit" class="wpcf7-submit" value="Send"><img src="http://[website-url-removed]/wp-content/plugins/contact-form-7/images/ajax-loader.gif" alt="Sending ..." style="visibility: hidden;" class="ajax-loader"></p>

With acceptance the input field changes to look like this

<p><input type="submit" class="wpcf7-submit" value="Send" disabled=""><img src="[website-url-removed]/wp-content/plugins/contact-form-7/images/ajax-loader.gif" alt="Sending ..." style="visibility: hidden;" class="ajax-loader"></p>

It appears disabled=”” is being introduced and this is causing issues (even though it is not disabled=”disabled”), if I edit the HTML with FireBug and remove the attribute then the form works as expected. I have tried disabling JavaScript and the output is the same, so it is not being generated via JS. I am guessing this is a bug however I need this form desperately as I am showing a client this website tomorrow! Any help would be hugely appreciated.

http://wordpress.org/extend/plugins/contact-form-7/