@GustuvWynd, did you ever find a resolution?
In my case I upgraded to 6.0.555 which broke my domain join. TM verified the problem and I will have a fix in a coming release.
In the meantime this issue is no longer a problem for me. All of the above methods to access the UNC (netbios host name, FQDN, DNS CName/alias, IP address) all work. Either it has been fixed or is related to the (now broken) domain join.