I use Weaver Xtreme on three sites. For as long as I can remember (years), when editing widgets each widget display shows some error message which is partly hidden.
One of the widgets is NextGen Gallery. When editing widgets, a PHP error is thrown from NextGen code saying that a variable widget_id is missing or undefined. I wouldn’t expect any widget to know its own id, so I wonder if this is something not being instated correctly or having the wrong scope within the theme.
It is a minor issue as I have work around it and ignore the errors. The widgets all display correctly on the working site(s).