ADMIN$ share unavailable over VPN

[cfapress]

From my 2003 server I am unable to browse workstations on other networks connected with site-to-site VPN.

For the sake of discussion, assume I'm authenticating with Domain Admin credentials.

Here's the set up:
Main Site --IPSecVPN--> Remote site
10.1.1.0 ------------> 10.1.2.0

A) The server at the main site cannot browse the default ADMIN$ share of any workstation at the remote site.

B) However, within the main site the server can browse ADMIN$ shares of local workstations
..and.. within the remote site a workstation can browse ADMIN$ shares of other local workstations

So, it would seem there's something in the VPN that's blocking the ADMIN$ share of the workstations.

C) BUT, remote site workstations have no_trouble browsing shares on the server including ADMIN$.

Given A, B & C ... what's going on here?!

Server = Windows 2003 R2
Workstations = XP Pro SP2/SP3
Routers = Linksys BEFVP41

Thanks in advance,
Jason Morrill
IT Manager