Matteo Legittimo on "[Plugin: Contact Form 7] After update "undefined function wpcf7_add_shortcode()""

After updating to the last version i get this error:

Fatal error: Call to undefined function wpcf7_add_shortcode()

I'm calling:

wpcf7_add_shortcode('postdropdown', 'createbox', true);

in my function.php
Before last update was working.
Can u help me please?
Thanks a lot

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