If you see the "spinning arrow", probably your problem have relation to Jquery or an incompatibility between the plugin and your theme. http://wordpress.org/support/topic/contact-form-7-continuous-spinning-arrows
By the other hand, I have a similar issue with the redirect solution.
I need people to go to an specific page, which is mostly unreachable if the user doesn't pass through the form first.(I'm using sessions for that).
The solution works perfectly in IE and Chrome, but is failing in Firefox, and I really can't see why. I'm beggining to despair.
To see the problem you have to pass through this URL
http://www.previsionsocial.gob.cl/subprev/?page_id=10129
Then go to http://www.previsionsocial.gob.cl/subprev/?page_id=10134/
The code I'm using in the "Aditional" area in Contact Form 7 is this:
on_sent_ok: "location = 'http://www.previsionsocial.gob.cl/subprev/?page_id=10134/';"
I'm used to see IE destroying everything around it, but Firefox? That's new, and worrying.
Please, Help!