Windows 7 - VPN Network Shared Drive Error Domain/Non-Domain Differences

I'm running into a problem with connecting to network drives over a VPN. The common difference is whether or not the computer is part of the domain by default.

1) Computers connecting to VPN using local account on computer: Prompted for a domain login when attempting to use the network drives. Can get in.

2) Computers connecting to VPN using a domain account (but on another network): Unable to connect. Specific error changed based on below info.
A) Computer logged on and connected to an outside network. Never connected to domain network: Can't find folder error.
B) Connects to domain network at some point before connecting to an outside network and using VPN: Might be in use error, attached.

Sounds more like the network the VPN connection puts you in has trouble making kerberos connections to domain controllers, but NTLM connections work fine (kerb might be blocked). The errors are likely bogus if you can get #1 to work - if the computer is connected to a domain it's going to want to use Kerb before NTLM, and if the machine still has (what it thinks is) a viable kerb ticket, it's going to try and validate that with a DC (to achieve auth), and if this fails, so does the connection.

This may not actually be the case, of course, but it sure has the symptoms of it.