In most cases this is name resolution issue. can you ping the DC using FQDN?
You may want to install a WINS server. Or this search result may help.
VPN Issues
Can't join domain over VPN because of using DHCP · Can't ping one of
VPN clients Can't ping external NIC while RRAS is active ...
www.chicagotech.net/vpn.htm
--
Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on
http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on
http://www.HowToNetworking.com
<richard.banham@gmail.com> wrote in message
news:10d52049-8372-4639-a0c5-bd9971e84b71@a1g2000hsb.googlegroups.com...
>I have a laptop running xp pro sp3 and I am working from home but have
> been able to join my company's domain when connected through VPN (some
> Juniper web based deal ... not a client). Anyway, the issue is that
> when I go to login to my PC I can see the corp domain but when I try
> to login I get
>
> The system cannot log you on now because the domain X is not available
>
> I KNOW if I drive the 8 hours to the office and jump on the network
> hard wired it would work but I don't want to have to do that...I
> really just need to figure out how to change my Logon Domain (keeping
> in mind that I have to be connected through VPN ... so I guess I'd
> need a command line trick or something).
>
> Below is a section of the results of "net config workstation"
>
> Workstation domain CORPNET
> Workstation Domain DNS Name corpnet.local
> Logon domain WKS-3WCR9GI
>
> I want to be on corpnet domain and I'm almost there. PLEASE HELP!