If you recently updated to .Net Framework 3.5 Service Pack 1?  Are you now seeing prompts when trying to install inbox printer drivers warning that the printers have not passed Windows Logo testing? Cause: The update includes the XPS Essentials pack, which installs an updated Unidrv.dll.  The Unidrv.dll binary provided in the update is not signed, which then causes all inbox printers to be unsigned.

A fix is available Microsoft KB Article 961118, which provides download links to the hotfix for the different OS versions that resolves the issue.

Source:→ TechNet Blog