Wait for your DNS stuff to fully propagate. It changes in DNS do not reflect immediately because there are a lot of DNS servers. Also, DNS follows some kind of hierarchy. Just be patient and wait a little longer.
If you cannot wait and you are using Linux or other *NIX OS, then just hardcode the frih.net IP address and your subdomain to /etc/hosts. Of course, this should be just temporary; just for checking if the subdomain actually works. I don't know how you can do this in Windows but you might as well try searching the net to check if it is even possible.
Your problem might have something to do with Server 2 accounts being moved to Server 3: http://www.frihost.com/users/Bondings/blog/vp-99580.html
I haven't added nor removed a subdomain recently after the news broke out so I don't really know if your problem is related or not. Anyway, you might want to contact Bondings regarding the matter.