AutoDiscover Certificate gives warning error from computers outside the network

I'm running Exchange 2007.  When Outlook users from outside our network open Outlook they receive a certificate warning.  It says that the certificate is valid and trusted, but "the name of the security certificate is invalid or does not match the name of the site".  I have two CAS servers configured with NLB.  My certificates has 3 names, cas1.domain.edu, cas2,domain.edu, jointname.domain.edu.  In DNS,  the autodiscover alias points to jointname.domain.edu.  I assume the warning is because it tries to use autodiscover.domain.edu and this isn't an actual altername name.  I've tried adding an SRV records per article:
http://support.microsoft.com/kb/940881, but it doesn't change anything.  I assume that is because the original attempt doesn't outright fail so that is tries the SRV record.  Aside from buying new certificates, doesn't anyone know how to make the warning go away. Outlook inside my network works fine - as does OWA.  This is specifcally related to Outlook Anywhere.
My test client is Outlook 2007, and think it will suffice to alleviate the warning just for Outlook 2007 if that is possible.
Thanks.