Issues with one trusted domain trying to VPN, error 812

We have 3 domains in our company.  Two can VPN in, but all the users in the other one receive an error 812.

We have checked:

1. Server side: Dial-in permission on their DC allows for access.

2. other domains, besides the main are able to authenticate.

3. client side has tried Auto and PPTP though PPTP is the only option enabled server side. When set to PPTP, he gets error 812, when set to Auto, he gets error 718.

I have done the client side trace files as suggested in another article, but I'm not getting much from the log.

Thanks,