i tried to setup an AD (active Directory as PDC) using the qnap TS-251 (with brings this feature by using samba 4). Currently fails the moving the client to the domain. Explaination below

the Setup is the following:

fritz!box
is doing the dhcp and also is the second DNS
IP is x.x.x.x.1

Qnap is doing the primary DNS
IP is x.x.x.x.31
primary DNS x.x.x.x.31 (qnap)
secondray DNS x.x.x.x.1 (Fritz!box)
AD is setup as muppet.local (Name)

Client is window 7 Ip comes from dhcp
DNS manual set to:
primary DNS x.x.x.x.31 (qnap)
secondray DNS x.x.x.x.1 (Fritz!box)
checked with ipconfig /all

nslookup fails with ? unkown type 41?
C:\Users\>nslookup muppet.local (root) ??? unknown type 41 ??? Server: UnKnown Address: 192.168.178.31 Name: muppet.local Addresses: 192.168.178.31 192.168.178.1

moving the client to the domain fails with Fehler: "Der DNS-Name ist nicht vorhanden." (Fehlercode 0x0000232B RCODE_NAME_ERROR)

I have already disabled ip V6 on the client.

Currently i can not move the client to the domaine. Any Ideas?