I used the technique suggested in your article here http://contactform7.com/tracking-form-submissions-with-google-analytics/
However, I found that is caused the form submission to break. When a user would click submit the "loading" animation would spin for a second then disappear without a confirmation message appearing and, in the end, the form did not send.
I tried two versions of the analytics code. I first tried the code as:
on_sent_ok: "_gaq.push(['_trackEvent', 'Contact Form', 'Submit']);" and this as:
on_sent_ok: "ga(‘send’, ‘event’, ‘Contact Form’, ‘submit’);”
If I remove this code it works perfectly. I'm currently running 3.6.1 but also had this issue on 3.7 (I had updated to 3.7 but reinstalled WordPress when I though the form submission was failing because the plug-in wasn't compatible with the new version).
Any idea what may be happening?