I installed a widget (specifically, Scott's example todo widget) through the admin interface with the .wgt file.
After using it and displaying it on a Moodle page with the plugin, I used the admin interface to delete the widget.
After deleting the widget, any attempt to access the Widget gallery resulted in an HTTP 500 error.
When attempting to close and restart the server, the following error was displayed, and the server wouldn't start:
/home/mark/public_html/wookie/wookie/ant/ivy-webapp-common.xml:45: The following error occurred while executing this line:
/home/mark/public_html/wookie/wookie/build.xml:45: The following error occurred while executing this line:
/home/mark/public_html/wookie/wookie/widgets/build.xml:71: /home/mark/public_html/wookie/wookie/widgets/todo not found.