Hello, and many thanks for your great work!
I am using WP 3.7.1, Contact Form 7 version 3.6 and Sweet captcha version 3.0.5. In contact form shortcode is not replaced by captcha, it stays as text.
If I use your built-in contact form, everything works well.
Page with the problem is here: http://imamaguru.ru/maminy-istorii/