I have 2 domains that reside in seperate states that are connected by a VPN tunnel with 6mb of bandwidth and using cisco equipment. I was able to setup DNS zones in each domain and have no problem loading the dns files from the masters. If I run NSLOOKUP from the 2003 DC and type the name of the remote domain i get the list of all the domain controllers in the remote domain.
However, when i go to create the trust though i get the error "Cannot Continue: The Local Security Authority is unable to obtain an RPC connection to the domain controller DC.DOMAIN.COM. I am able to ping both the domain controllers by their name and the domain names themselves in each direction. When i ping the domain name it returns the address of the DC that is SOA for that domain. I am stumped so if anyone has any suggestions please let me know.