Issues accessing file shares of certain servers across site to site VPN

Question

We recently had a problem crop up with one of our remote facilities, i'm not a system admin, and we are currently without one, but I will try to explain the best I can.

Employees at the remote site are not able to access some of the servers here with file shares. The remote site connects to our main site here through a Cisco ASA 5505 VPN, the remote site has its own domain controller, DC4, which should be replicating with the DCs at the main site, DC1 and DC5.

All our shared network drives are hosted on a server, FILE1, that is at the main site. Trying to browse to that server using \FILE1 gives the error "Target logon name is incorrect". nslookup and pinging FILE1 from DC4 by both hostname and IP address work, and browsing to the file shares from \ works just fine. There are also some servers which are able to be browsed completely fine by hostname, or IP, and another server that cannot be browsed to by either.

Looking at the event viewer for DC4 at the remote site, there are a lot of Kerberos error 4 listed under the system tab.

Accessing the main DC from DC4 results in the same "Target logon name is incorrect" error, but the reverse works just fine. I can get to file shares on DC4 from DC1 or DC5 at the main site.

DC4 and DC1 are running Windows Server 2003, and DC5 is running Windows Server 2008 R2.

Any help would be GREATLY appreciated!