Error when adding widget

Installed and activated plugin. New Widgets in Navigation Menu area shows up under Widgets. However when I add a Widget, in this case I tried the Jetpack Subscriber Widget as well as the Google translator Widget, and I press the Save/Update button (top right) it gives an error message [object, object] on left bottom of screen and hangs (the Save/Update button remains waving).
I already tried deactivating and removing plugin, new area and reinstalling everything, however with the same result.
Hope you can help as I really love the functionality!
Cheers, André Huizing

The page I need help with: [log in to see the link]