User can not see the whole content of share folders

Hi 
There is a share folder on windows Server 2008R2 Sp1. All users can create files and folders in our share folder but some of users can not see the whole files and folders in share folder in the same time. They have to restart their clients to see those files and folders.
It happens randomly.
My Domain's FFL and DFL is 2008R2 and the clients use windows 7Ultimate or Professional.
any idea . . .