I have a similar issue. Last time I tried to update WPDM I received the same message as this time: An error occurred while updating Download Manager: The package could not be installed. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature.
Why is it so hard to update this plugin? I logged out and back in, still no luck. Do I have to delete the plugin and then reinstall it?