on_sent_ok not working in Contact Form 7 normally indicates a Javascript conflict with either your current WordPress theme or one of the other plugins you are using - see Contact Form 7 Email Issues - there is a link there that covers Javascript Conflicts.
Remember that a problem in one script can cause issues in another. For example, some jQuery errors can stop jQuery processing any more script, which can make the culprit hard to find.
A jQuery error in one of your plugins or your themes javascript files can stop jQuery processing before it gets to the CF7 script.
Use Firebug or Chrome Dev Tools to examine Javascript conflicts in detail.
See http://wiki.simple-press.com/installation/troubleshooting/plugin-conflicts/ for general guidance.