Peer to Peer Networking Issue

We have two Vista computers. We keep our files on a Desktop

computer and use peer to peer networking to access them from

the laptop. Every once in a while, the desk top will not allow the

laptop to save a file it has open. And the desktop will not shut

down or restart. It will not shut down and has to be physically

powered down.

Once the desktop has rebooted everything returns to normal even

if the document is still open on the laptop.

This issue did get better with one of the updates in July, but

it still happens.

Any ideas? Microsoft did not have anything useful except to

uninstall Anti-virus to see if that was it.