Outlook Anywhere - HTTP 403 forbidden

We are in the process of migrating from Exchange 2007 to Exchange 2010 but I can't get Outlook anywhere to work. When I run ExRCA, I get the following error during Testing HTTP Authentication Methods:

I get the 403 error internally as well if I try to go directly to the https://internalmailservername.company.com/rpc

All other services such as autodiscover and activesync work just fine. I am using a wildcard cert. I have tried setting the OutlookProvider certprincipalname for EXPR but still no luck. IIS configuration follows http://msexchangeguru.com/2010/10/05/autodiscover/. I'm using Basic Authentication for Outlook Anywhere. All traffic to the CAS array is routed through a Netscaler.

Any ideas?

Testing HTTP Authentication Methods for URL https://mail.domain.com/rpc/rpcproxy.dll?outlook.domain.com:6002.
	The HTTP authentication test failed.
	Additional Details   An HTTP 403 forbidden response was received. The response appears to have come from Unknown. Body of the response: You do not have permission to view this directory or page.