widget form disappearing

I am in the process of creating my first widget/plugin. The problem I am having is that every time I drag my widget into a sidebar it saves and then the form disappears. Actually every widget does this now and I am pretty sure it is caused by something that I have done. If I click save again on the widget or if I refresh the page the form comes back but the defaults that I have set in the form are not longer there.

Does anyone know what the problem could be?