How can I stop MS Word from prompting for credentials every time I open a document from my claims/ADFS SP2010 Extranet site?

We have a SharePoint 2010 extranet site which uses claims-bassed authenticate (ADFS). While external stakeholders need only authenticate once through the browser (because their browsers cache their SAML token), the behavior with MS Word is very different: event time we open a Word doc we are prompted for credentials.

Is there any way to change this behavior so Word will either use the credentials stored in the browser or at least remember the credentials after the initial challenge?

Thanks

Aa

______________ Aaron Hamilton