In Jetpack Version 2.5
The Widget Visibility feature and the
WP Core Contributions Plugin Version 1.2.2 has a conflict in the widget layout.
See Screenshot http://cl.ly/image/190S3m303Q24
Once the Widget Visibility feature is deactivated the conflict with Core Contributions Plugin goes away.
I am making an educated guess this this a Jetpack issue as the Core Contributions Plugin fits the layout fine without the Widget Visibility feature.