can’t copy some files from nt 4.0 server

i want to copy some files to my client computer from nt 4.0 server but i can’t .it gives an error message. i even can’t rename or delete these files. the error message is
— the files couldn’t be copy

but when i go up to server and copy it from there to my shared harddrive, there is no problem
i can copy these files

what is the problem ?
i see this problem some nt 4.0 servers also