Windows 7: Windows 7 Domain Computers Problem with copies to network drives

Hello,

I work in a company with almost 80 Windows 7 computer and another 200 or 250 Windows Xp computers in the domain, sometimes when users try to copy information to the File Server (Windows Server 2008) or to the network, the copy starts but never finish. It just stay there and the only way is to force the shut down to the computer and start over copying files one by one, this only happens in Windows 7 computers and does not always happen but it is very common

Is this a Know issue in Windows 7? What can be happening in our Network??



If I try to do the same copy locally on the computer the copy ends successfully, the problem only hapends when the copy is to the network (Just Windows 7 computers, Xp computers works fine)

Thank you all.