Multiple Upload Documents menu option missing for doc libs using extranet URL

Hi,

I do not know if the following is ExCM related or not however, symptoms indicate this issue may be related.  Please excuse this if it is not ExCM related.

When I access our site using our internal URL to the site (e.g. http://extranet.internaldomain.com/sitename), go to a document library, I can select the Upload button and see to options: Upload Document and Upload Multiple Documents.

When I access the same site using the external URL to the site (e.g. https://extranet.externaldomain.com/sitename), sign in using an FBA account with contributor rights to the site, access the same document library, and select the upload button I only get one option: Upload Document.

This does not happen on our other SharePoint web applications, but all others that I manage are strictly internal.

I have pored through the SharePoint and ExCM settings, and have not been able to find the root cause.

Has anyone else seen this irregularity?