Custom widget backend form disappears.

I have created a plugin which creates a custom post type, taxonomy, fields and a widget.

The result is positive at the frontend, like you can see the Our work section on gagawalagraphics.com homepage. You can check out the plugin code on github.
The widget is able to load the portfolio items.

The only problem am facing is am not able, update the widget’s settings at the backend because it’s form disappears, if I navigate away from the widget’s dashboard. And when I navigate back, all I can see is the widget title but not form fields.
See backend screen shot when am adding the widget first time.
Click here please.

See backend screen shot when I navigate back to the widget dashboard.
Click here please.

Please advise on what I could have done wrong.