Accessing files on Vista network share breaks network

I recently did re-install of Windows 2000 pro on a workstation in my
workgroup. When I try to copy files located on my Vista box, Windows
Explorer (on the Win2000 box) hangs, and somehow, my connection to the
network (lan, internet, everything) on the Vista box is broken, and I need
to re-boot the Vista box to be able to connect to the network again.

This did not happen before the new installation of Win2000 - It worked fine
before the re-install.

Also, If I use the Vista box to do the file transfer, it works fine - I have
the problem only when I do it from the Win2000 box.

Anyone have an idea of what might be going on here?