Vista RTM Network Authentication and VPN problem

I have a Vista RTM workstation on a WinSrv2003 domain (call it Domain1) and
I'm logged on as domain1\jthorne. When I make a VPN connection to another
domain (Domain2, logged on as domain2\jthorne), I have a problem on Domain1.
When a mapped drive letter auto-disconnects, it cannot reconnect because the
workstation sends the wrong network credentials. I can see in the server
security log that domain2\jthorne tried to connect.

What do I do to make Vista send the right credentials? If I disconnect the
VPN, then everything on Domain1 starts working again.

--
Jim Thorne
Information Systems Manager
Aguila