Appointments + makes whole website down, need quick support

Warning: call_user_func_array() expects parameter 1 to be a valid callback, class 'Appointments' does not have a method 'post_ceontent' in /home/kinesan/public_html/wp-includes/plugin.php on line 235

Since update to 1.7.1 I have this line appearing on all my webpages.

I have to deactivate appointments+ to get my website live back on

Thanks