Hi Kevin I checked the server setting, and cURL is installed. It was also necessary for the plugin I use to embed the Facebook wall. But the problem occurred even before I add this plugin. I don’t think they are in conflict.
But remember it is not only the case for the newsletter form.
I got exactly the same problem with the contact form as well.
That’s why I thought it was more related to ajax script behind. At the beginning, I had nothing set in newsletter settings and the form never shown an error message with email address filled-in.
It really a matter of “loosing the click ability” while every fields are good…