I had updated to 2.0, which had many bugs and rendered the email sign-up feature mostly useless for the last couple weeks. I just updated to 2.1, which fixes the core features (using just the API widget), but the form designer / widget do not work. When I try to design a form, I can create / save a new form, but I cannot see the form itself. I had this problem using Chrome and FF.
I would suggest removing the form designer feature altogether, or ensuring that the bugs are worked out in the next release.