How does the crm snapin authenticate the user? Does it check settings in registry, one of the SQL databases (which one?), Active Directory, ADFS, ...? This will at least point me into some direction to more closely investigate.
Btw, in a previous installation this did work just fine. The difference this time is that ADFS is installed on the CRM server running on Server 2008 instead of being installed on the SBS server. ADFS 2.0 was installed by directly downloading it rather than
through the roles (same way as I did it on SBS before).