The error (A Web Part or Web Form Control on this Web Part Page cannot be displayed or imported because it is not registered on this site as a safe control) indicates a problem with the installation (deployment) of the product, ie: a necessary file was not deployed successfully to all Web Front Ends, or our Code Access Security policy was not applied successfully to the Web Application(s).
To resolve, please reinstall the product using one of the following methods:
- In Central Administration > Operations > Solution Management: Retract and the re-Deploy the solution (.wsp) to your Web Applications
- Using the product installation scripts, uninstall and reinstall the product
- NOTE: resetting IIS and the WSS Timer service on all farm servers running the SharePoint Web Application service can help, before installing (deploying) a product into SharePoint