The trust relationship between this workstation and the primary domain failed - Trouble Shooting...

Win 7 RC 7100 new install, joined to 2000 Server SP4 AD Domain. When I try to add a domain user account to 7, errors : " The trust relationship between this workstation and the primary domain failed ". ( Already have 2 x 7RC machines joined, incl my primary workstation: I like 7 ). I have multiple times left/rejoined the domain, even: joined the machine to a Work group, deleted machine account from AD, booted up as work group user, added machine name to AD, waited 20 mins, rejoined 7 to Domain, booted in as Domain user, tried to add another user, always same prob. Left domain, changed PC name, rejoined, same. Local ip settings for DNS are correct (below). No network mapped drives. Network browsing is fine. Same prob with diferent user acounts. ipconfig /release, /renew, same. Stumped. Thanks!

btw Posting from Firefox gives "Unknown Error". From IE8 works. Much could be said about that.
>ipconfig /all

Windows IP Configuration

Host Name . . . . . . . . . . . . : EPHEMERAL
Primary Dns Suffix . . . . . . . : naitauba.local
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : naitauba.local

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : naitauba.local
Description . . . . . . . . . . . : Intel(R) PRO/1000 CT Network Connection
Physical Address. . . . . . . . . : 00-0C-F1-A1-E9-4C
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::a183:b8e1:574a:46fb%11(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.0.27(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.254.0
Lease Obtained. . . . . . . . . . : Thursday, June 25, 2009 3:09:56 PM
Lease Expires . . . . . . . . . . : Saturday, July 25, 2009 3:09:55 PM
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.4
DHCPv6 IAID . . . . . . . . . . . : 234884337
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-11-C0-6B-52-00-0C-F1-A1-E9-

DNS Servers . . . . . . . . . . . : 192.168.0.11
192.168.0.10
NetBIOS over Tcpip. . . . . . . . : Enabled

Tunnel adapter isatap.naitauba.local:

Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : naitauba.local
Description . . . . . . . . . . . : Microsoft ISATAP Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes