Windows 7 / Vista loses local resources when connected to VPN

When connected to a pptp VPN resources on the local domain are
inconsistantly available. Previously with XP they were always available even
if connected to a VPN.

What has changed?

From win 7, I can print to a Lan printer shared on the server (2008)
Once connected to a remote VPN (windows 2003 pptp), the print que says
"Accessed Denied" when trying to print to the same printer.
With XP printing was still possible to the Lan even though connected to a VPN.

Mapped Drives:
Sometime they work, sometimes they don't. If I have a mapped drive to a
local file server once connected to the VPN I can't list the contents of
drive, or access any of the files.
Other times even with a VPN connected I can acess the files. If you access
the drive before opening the VPN this seems to help.

I thought it may be a DNS issue but I have added the server to my hosts
file. The host name resolves correctly even after an "ipconfig /flushdns".

Does windows 7 need to resolve service records on the local AD dns server
before passing on credentials? The order of accessing DNS servers is the
remote VPN DNS server first and then the local DNS server second. Is this why
I can always print to a local printer that I installed using its IP address,
whilst connected to a VPN, which then prompted me for credentials. I assume
the credentials were stored locally, making them always available no matter
what the order of DNS servers were.

Once connected to a VPN why can't Vista/Win7 always print/access local
Connected to the same VPNs XP could always access local recources.
Whats changed?