This is most likely due to 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.
Could be other email issues which are also covered in the link.
Thank you! I’ll try to figure that out 🙂
Yes I fix it. I had a problem with a required field that doesn’t appear on the contact form (strange that I didn’t notice the absence :D). And I inspect the form with firebug under scripts I saw the message that a required field isn’t completed. And the error message wasn’t there because the entire field is missing.
Thanks guys 😉
Cheers