We have made the difficult to decision to discontinue support for the Silverlight version of WebViewer. In recent years, plugin-based web development has been largely overtaken by HTML5. The plugin developers themselves have essentially ceased to develop or support the plugins. Bugs in the Silverlight version of Webviewer can usually be traced back to a bug in Silverlight itself, and our efforts to have these fixed by Microsoft have been met with silence or an explicit "will not fix". For this reason, we have decided that it has come time to retire the Silverlight version of WebViewer (formerly known as SilverDox).
The good news is that we offer a near-seamless update path to HTML5 with the HTML5 version of Webviewer. The HTML5 version offers the same features as the Silverlight version, renders .xod documents, and has many additional features such as easier customization, support for encrypted documents, more annotation types, mobile device compatibility with a mobile-specific UI, and support for forms.
Please let us know if you have any thoughts on this announcement, or need any help in getting started with the HTML5 version.