Error code -51 (try to copy from win to mac)

Hi,

I have a problem with copying files FROM Windows to my Mac. I am connected through the VPN, I can see files on Windows server, I can copy TO server, I can create folders etc (on Win), but if I try to copy from Windows I always get "errorr code -51". I have MacBook Pro with Snow Leopard 10.6.8.

Does anyone know what is going on? Thankx a lot, Lukas