Copy from Network Problem

I have a smal business Network , and one of the computers
can't copy the files from a shared folder (folder ADV ) in the Server.
( 5 computers)
The "problem computer" , can copy anything from and to
anywhere , but when it copies from folder ADV in the Server ,
I get the message that "network path is no longer valid "
All running WinXP Pro , SP2 ; The drives are not
mapped ( and even when I try to Map them I get the same message )
I formatted the "problem computer " , and the message
still comes back .
Scandisked Sever and the remaining 4 computer .
There is no Firewall ( Internal Network )
All other computers copying to and from any shared folder
normally .
Hints ?