File Open Dialog - get rid of "Do you wish allow..." alert popup?

Hi folks,

We have successfully implemented the file open dialog in our edit workflow in order to add attachments, but we'd really like to skip the Alert 'Do you wish to allow the Silverlight plugin access to your local filesystem?" message. This is not great UI design and I really don't want to deploy this workflow for the client (a very large US city government site) and require them to click OK every single time. Thanks in advance for your help!

Cassandra