After installing version 1.5.1 on the production server some days ago our editors encountered a problem with the default widgets after saving a new post or page.
The widgets set on the settings page "Default Widgets" (.../wp-admin/edit.php?post_type=widget&page=ww-defaults) do not appear after saving a new page. But checking option 'Reset this page to the default widgets.' and saving again will bring the default widgets to appear in the sidebar area.
Also another feature fails now. In the list of diabled widgets on the post edit page each widget entry has a select field on the right side (e.g. Disabled | Sidebar1). Selecting Sidebar1 for the widget results in disappearing the widget from the Disabled list but does not appear in the list of Sidebar1. This behaviour also appears on the "Default Widgets" settings page.