Your subscribe form seems to miss some kind of closing tag or has an other coding error. Because if it is not the last widget in the sidebar then the next two widgets are displayed outside to the right of the sidebar.
I´m using Fusion theme and your widget is the only one with this kind of behaviour. The problem occurs in IE7, not in firefox.
Another question: Why does it need so long until the e-mail form is displayed? Other elements in your widget are visible directly and the form field(s) seems to be only visible after the last elements on page loaded!?
Thanks for feedback / solution.