Connection Lost. Saving disabled…

I too am experiencing this issue. In my case, when I attempted to edit a page, the “Connection Lost…” dialog immediately appeared. At first, I thought it might be a conflict with a similar plugin (Email Subscribers & Newsletters, which BTW, has some features that I wish Constant Contact Forms has), but when disabled the Constant Contact plugin, the problem disappeared. For now, I’ve deleted the Constant Contact Forms plugin, sadly.