Configuring Server Bindings for SSL Host Headers (IIS 6.0):

In addition to installing a wildcard server certificate on SSL-enabled Web sites, you must also configure the SecureBindings metabase property on each site so it contains the host header name of the site. All SSL-enabled sites that use the same IP/port binding and are distinguished only by host header name must use the same wildcard server certificate.

I guess it's nice that even though this property isn't editable via the GUI that there is a way to set it with what is required, but it just seems like such an odd thing to have to do. Especially since I'd expect to be able to set the hostname in my WCF code and/or configuration and not have to touch IIS, perhaps this is "fixed" in IIS 7...