Live preview not working, also, unable to add Media

Hi There,

i recently installed the e-Newsletter plugin and I'm having trouble with the live preview, It just won't show. Sending a Preview E-Mail works though.

I Noticed that, when i save, ajax request fired with action: customize_save, doesn't get any response. Is that suposed to be so?

The add Media Button also dosen't work. It throws a javascript error (TypeError: n is undefined in Underscore.js, wich is a core file).

I'm using wordpress 3.6, and I already deactivated all plugins but e-Newsletter.